Motivation:
We've seen IllegalReferenceCountException from this test. This is
probably not the root cause, but the root looks like it is lost in the
pipeline.

Modification:
- Increase the test timeouts.
- Add sync() calls so we make sure to wait for the event loop shutdowns
to complete, before we close the scope of the LeakPresenceDetector.
- Change an assertNotSame call in a future listener (which runs on the
event loop) with code that captures the error and funnels it out to the
test code through a future.

Result:
More debuggable test, maybe more stable too.

(cherry picked from commit 82a1f0e)