Find the timer thread and assert it's gone after invocation
Find the timer thread and assert it's gone after invocation

We don't control the threads created/destroyed while our test is running so let's
just find the one we care about and make sure it's gone after the invoker completes.

Fixes #10222


(transferred from ManageIQ/manageiq@c24acb20590fe89f97ec7a4f58f4c2237296c8b9)

bdunne/manageiq-automation_engine