Flaky test homepage app sample data uninstall should uninstall sample data set

[LeeDr]

Kibana version: master

Elasticsearch version: 7.0.0-alpha1

Server OS version: Ubuntu 16.04 (Jenkins worker)

Browser version: Chrome

Browser OS version:

Original install method (e.g. download page, yum, from source, etc.):

Describe the bug:
This test failed on Jenkins with Error: expected true to equal false which is from the expect right after this line;
https://github.com/elastic/kibana/blob/master/test/functional/apps/home/_sample_data.js#L106

We can see from the failure screenshot that the notification "Sample flight data uninstalled" is visible, but it also still shows "Sample flight data" is installed. Is it just a timing problem and has to keep checking for a bit to see if it changes state?
The previous expect in this test is within a retry.try() loop, and maybe this check should also be?

Steps to reproduce:

1. run a PR with only a Docs change (nothing that should impact this test)
2. this test failed :-(

I don't know how often this test fails?

Expected behavior:
This test should pass unless someone broke the code

Screenshots (if relevant):

homepage app sample data uninstall should uninstall sample data set.html.txt

Errors in browser console (if relevant):

Provide logs and/or server output (if relevant):

16:32:33    │ proc  [ftr]      └-: uninstall
16:32:33    │ proc  [ftr]        └-> "before all" hook
16:32:33    │ proc  [ftr]        └-> should uninstall sample data set
16:32:33    │ proc  [ftr]          └-> "before each" hook: global before each
16:32:33    │ proc  [ftr]          │ debg  TestSubjects.click(removeSampleDataSetflights)
16:32:33    │ proc  [ftr]          │ debg  TestSubjects.find(removeSampleDataSetflights)
16:32:33    │ proc  [ftr]          │ debg  findByCssSelector [data-test-subj~="removeSampleDataSetflights"]
16:32:33    │ info  [o.e.c.m.MetaDataDeleteIndexService] [VuWBRUp] [kibana_sample_data_flights/_N7zXZFJSS2WNceKuMcYnw] deleting index
16:32:33    │ proc  [ftr]          │ debg  TestSubjects.exists(sampleDataSetUninstallToast)
16:32:33    │ proc  [ftr]          │ debg  existsByDisplayedByCssSelector [data-test-subj~="sampleDataSetUninstallToast"]
16:32:33    │ info  [o.e.c.m.MetaDataIndexTemplateService] [VuWBRUp] adding template [kibana_index_template:.kibana] for index patterns [.kibana]
16:32:33    │ info  [o.e.c.m.MetaDataIndexTemplateService] [VuWBRUp] adding template [kibana_index_template:.kibana] for index patterns [.kibana]
16:32:33    │ info  [o.e.c.m.MetaDataIndexTemplateService] [VuWBRUp] adding template [kibana_index_template:.kibana] for index patterns [.kibana]
16:32:33    │ info  [o.e.c.m.MetaDataIndexTemplateService] [VuWBRUp] adding template [kibana_index_template:.kibana] for index patterns [.kibana]
16:32:33    │ info  [o.e.c.m.MetaDataIndexTemplateService] [VuWBRUp] adding template [kibana_index_template:.kibana] for index patterns [.kibana]
16:32:33    │ info  [o.e.c.m.MetaDataIndexTemplateService] [VuWBRUp] adding template [kibana_index_template:.kibana] for index patterns [.kibana]
16:32:33    │ info  [o.e.c.m.MetaDataIndexTemplateService] [VuWBRUp] adding template [kibana_index_template:.kibana] for index patterns [.kibana]
16:32:33    │ info  [o.e.c.m.MetaDataIndexTemplateService] [VuWBRUp] adding template [kibana_index_template:.kibana] for index patterns [.kibana]
16:32:33    │ info  [o.e.c.m.MetaDataIndexTemplateService] [VuWBRUp] adding template [kibana_index_template:.kibana] for index patterns [.kibana]
16:32:33    │ info  [o.e.c.m.MetaDataIndexTemplateService] [VuWBRUp] adding template [kibana_index_template:.kibana] for index patterns [.kibana]
16:32:33    │ info  [o.e.c.m.MetaDataIndexTemplateService] [VuWBRUp] adding template [kibana_index_template:.kibana] for index patterns [.kibana]
16:32:33    │ info  [o.e.c.m.MetaDataIndexTemplateService] [VuWBRUp] adding template [kibana_index_template:.kibana] for index patterns [.kibana]
16:32:33    │ info  [o.e.c.m.MetaDataIndexTemplateService] [VuWBRUp] adding template [kibana_index_template:.kibana] for index patterns [.kibana]
16:32:33    │ info  [o.e.c.m.MetaDataIndexTemplateService] [VuWBRUp] adding template [kibana_index_template:.kibana] for index patterns [.kibana]
16:32:33    │ info  [o.e.c.m.MetaDataIndexTemplateService] [VuWBRUp] adding template [kibana_index_template:.kibana] for index patterns [.kibana]
16:32:33    │ info  [o.e.c.m.MetaDataIndexTemplateService] [VuWBRUp] adding template [kibana_index_template:.kibana] for index patterns [.kibana]
16:32:33    │ info  [o.e.c.m.MetaDataIndexTemplateService] [VuWBRUp] adding template [kibana_index_template:.kibana] for index patterns [.kibana]
16:32:33    │ info  [o.e.c.m.MetaDataIndexTemplateService] [VuWBRUp] adding template [kibana_index_template:.kibana] for index patterns [.kibana]
16:32:33    │ info  [o.e.c.m.MetaDataIndexTemplateService] [VuWBRUp] adding template [kibana_index_template:.kibana] for index patterns [.kibana]
16:32:33    │ info  [o.e.c.m.MetaDataIndexTemplateService] [VuWBRUp] adding template [kibana_index_template:.kibana] for index patterns [.kibana]
16:32:33    │ info  [o.e.c.m.MetaDataIndexTemplateService] [VuWBRUp] adding template [kibana_index_template:.kibana] for index patterns [.kibana]
16:32:34    │ proc  [ftr]          │ debg  TestSubjects.exists(removeSampleDataSetflights)
16:32:34    │ proc  [ftr]          │ debg  existsByDisplayedByCssSelector [data-test-subj~="removeSampleDataSetflights"]
16:32:34    │ proc  [ftr]          │ info  Taking screenshot "/var/lib/jenkins/workspace/elastic+kibana+pull-request+multijob-selenium/kibana/test/functional/screenshots/failure/homepage app sample data uninstall should uninstall sample data set.png"
16:32:34    │ proc  [ftr]          │ info  Current URL is: http://localhost:5620/app/kibana#/home/tutorial_directory/sampleData?_g=()
16:32:34    │ proc  [ftr]          │ info  Saving page source to: /var/lib/jenkins/workspace/elastic+kibana+pull-request+multijob-selenium/kibana/test/functional/failure_debug/html/homepage app sample data uninstall should uninstall sample data set.html
16:32:34    │ proc  [ftr]        └- ✖ fail: "homepage app sample data uninstall should uninstall sample data set"
16:32:34    │ proc  [ftr]        │        Error: expected true to equal false
16:32:34    │ proc  [ftr]        │         at Assertion.assert (node_modules/expect.js/index.js:96:13)
16:32:34    │ proc  [ftr]        │         at Assertion.be.Assertion.equal (node_modules/expect.js/index.js:216:10)
16:32:34    │ proc  [ftr]        │         at Assertion.(anonymous function) [as be] (node_modules/expect.js/index.js:69:24)
16:32:34    │ proc  [ftr]        │         at Context.it (test/functional/apps/home/_sample_data.js:107:32)
16:32:34    │ proc  [ftr]        │         at <anonymous>
16:32:34    │ proc  [ftr]        │         at process._tickCallback (internal/process/next_tick.js:188:7)
16:32:34    │ proc  [ftr]        │       
16:32:34    │ proc  [ftr]        │       
16:32:34    │ proc  [ftr]        └-> "after all" hook
16:32:34    │ proc  [ftr]      └-> "after all" hook
16:32:34    │ proc  [ftr]    └-> "after all" hook

Any additional context:

[liza-mae]

Also seeing this fail on 6.4.0 BC2 on cloud.

Link to console:
https://internal-ci.elastic.co/view/Stack%20Tests/job/elastic+estf-cloud-kibana+master/4/consoleFull