allow customizing docker registry

[tareksha]

Description of changes:

Allow the consumer to specify an alternative docker registry in the helm chart. This allows installing OpenDistro in non-public environments that rely on private docker registries. Keep the default as the standard implicit docker registry: docker.io

Test Results:

Image in templates/elasticsearch/es-data-sts.yaml with default values:

image: docker.io/amazon/opendistro-for-elasticsearch:1.9.0

Image in templates/elasticsearch/es-data-sts.yaml with setting global.registry=my.registry.org in values:

image: my.registry.org/amazon/opendistro-for-elasticsearch:1.9.0

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[gaiksaya]

Hi @tareqhs ,

Thank you for your contribution. I can see that you have not included any test results in the PR body. We would like you to share the test results and to see if this change causes any issues or any breaking changes.

[tareksha]

Hi @gaiksaya , added result from local tests

[gaiksaya]

Thank you for contributing!

[tareksha]

thank you @gaiksaya & @peterzhuamazon . when is this expected to be released?

[peterzhuamazon]

@tareqhs it will be included in the next upcoming release. Thanks.

[NovikovEvgeny]

Hi,

is there any way to pull only specific image from the private registry, but keep pulling other images from the default registy?

Use case: we use own ODFE docker image with additional plugins installed (download it from the private registry), but want to use default kibana image and default busybox (and other helper images) from docker.io

In helm chart version 1.9.0 and lower we just used

elasticsearch.image: privateRegistryName/imageName:imageTag
kibana.image: amazon/opendistro-for-elasticsearch-kibana:1.9.0

but now helm chart forces us to have all images in the same registry...