Fix Search Applications bug where deleting an alias before deleting an application intermittently caused errors

[kderusso]

There is an intermittent error when deleting search applications, where if the alias has been removed the search application deletion call can fail with an alias not found error.

To reproduce:

PUT example-index

PUT _application/search_application/test-sa
{
  "indices": ["example-index"]
}

POST _aliases
{
  "actions": [
    {
      "remove": {
        "index": "example-index",
        "alias": "test-sa"
      }
    }
  ]
}

DELETE _application/search_application/test-sa

It appears there is a race condition. Sometimes this returns an acknowledged response but other times it returns the following error:

{
  "error": {
    "root_cause": [
      {
        "type": "aliases_not_found_exception",
        "reason": "aliases [test-sa] missing",
        "resource.type": "aliases",
        "resource.id": "test-sa"
      }
    ],
    "type": "aliases_not_found_exception",
    "reason": "aliases [test-sa] missing",
    "resource.type": "aliases",
    "resource.id": "test-sa"
  },
  "status": 404
}

This PR addresses this.

[elasticsearchmachine]

Hi @kderusso, I've created a changelog YAML for you.

[elasticsearchmachine]

Pinging @elastic/search-relevance (Team:Search - Relevance)

[elasticsearchmachine]

Pinging @elastic/ent-search-eng (Team:SearchOrg)

[demjened]

LGTM

[carlosdelest]

👍

[elasticsearchmachine]

💚 Backport successful

Status	Branch	Result
✅	8.13