[Inference API] Fixing flaky test for auth integrationt tests

[jonathan-buttner]

This is a follow up to: #139978

The tests were muted for a different reason. The issue was that we're adding an empty response before each test is run. The problem with that is the node some times starts (and the authorization task that would call the mock web server and get the empty response) before the @Before method within AuthorizationTaskExecutorIT is executed. This means we'd enqueue an empty response after the authorization task has attempted to retrieve the empty response, then when the test runs we'd enqueue another response. The test would retrieve the empty response and cause a failure.

I tried making the mock webserver a member and have it initialized whenever the node was started but that was resulting in null pointers within some of the tests. I'm opting for enqueuing an empty response right before a node is started and then also clearing the response queue within each test prior to enqueuing the response we expect.

[elasticsearchmachine]

Pinging @elastic/search-inference-team (Team:Search - Inference)

[elasticsearchmachine]

💔 Backport failed

Status	Branch	Result
❌	9.3	Commit could not be cherrypicked due to conflicts

You can use sqren/backport to manually backport by running backport --upstream elastic/elasticsearch --pr 140321

[jonathan-buttner]

💚 All backports created successfully

Status	Branch	Result
✅	9.3

Questions ?

Please refer to the Backport tool documentation