Remove some sleeps from change feed test.
Remove some sleeps from change feed test.

Couldn't remove all sleeps as they are also used to
assert that nothing happened in a period of time or
to track generalized progress over a period of time
(the heartbeat test).

Issue #630

fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb