Cherry-pick #21461 to 7.x: Send updating state

[michalpristas]

Cherry-pick of PR #21461 to 7.x branch. Original message:

What does this PR do?

This PR reports updating state of application after update process is started and error in case it is finished with failure

Tested with elastic/kibana#78810 after suggested changes (i did them manually) i started agent without starting a file server so UPDATE fails i got this (as expected)

UPDATE is ACK-ed and Error there is reported, under ACK there is line saying STATE was switched to UPDATING

after i started server and rekicked UPDATE action

update was ACKed and state switched to RUNNING after it finished.

Status on list page was ONLINE then UPDATING and then back ONLINE. Even though there were errors, so i guess this will be an object of next iteration.

Why is it important?

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

[elasticmachine]

Pinging @elastic/ingest-management (Team:Ingest Management)

[elasticmachine]

💚 Build Succeeded

Expand to view the summary

Build stats

• Build Cause: [Pull request #21530 opened]

• Start Time: 2020-10-05T15:37:19.203+0000

• Duration: 37 min 38 sec

Test stats 🧪

Test	Results
Failed	0
Passed	1384
Skipped	4
Total	1388

[blakerouse]

Backport looks good.