rworker_service_creation is unstable

The test fails with:

431: 13:36:17   2.4s: TEST_FAILED! Test terminated with exception: 400: [

431:     {

431:         "detail": "A thread is being terminated, a change in the number of threads cannot currently be made."

431:     }

431: ]

This looks like a potential "race condition" in the test where it doesn't wait for the thread state to change or it lacks retrying. The failure is expected so it's just an error in the test itself.