Add test to ensure modified objects replicate.

Ensure that objects, when modified, actually replicate correctly to the
sink cluster.
Add test detecting source deadlock.

Add test which ensures that the AAE source worker doesn't deadlock when
waiting for responses from the process which is computing the hashtree
differences.

Unfortunately, this test uses timeouts because as the code currently
stands, I can't figure out a way to make it any cleaner.
Use correct intercepts.

Correct a typo which was causing the module to attempt to use intercepts
which do not exist.