[FEATURE] Integration Testing for AD Extension

[owaiskazi19]

Is your feature request related to a problem?

With the current development of AD Extension on feature/extensions integration tests were commented to achieve the development work of AD Extension. This issue addresses such tests present here. Will keep on updating this issue as and when the tests have been covered.

• [ ] SearchAnomalyResultsActionTests
• [ ] IndexUtilsTests

Other tasks needed for IT:

• [x] Use test cluster setup from SDK from https://github.com/opensearch-project/opensearch-sdk-java/issues/589 to setup the local test cluster to run integration tests
• [x] Create sdkRestClient() in OpenSearchIntegTests and use it for the integ tests of AD Extension.
• [x] create sdkClusterAdmin() for use in ADIntegTestCase
• [ ] create sdkClusterService() for use in ADIntegTestCase
• [x] create sdkAdmin() for use in ADIntegTestCase

[minalsha]

@joshpalis whats pending here?