Fix sporadic cluster_t test failure
Fix sporadic cluster_t test failure

The test was failing because a GC sweep wasn't happening. This fix
ensures that the GC does a pass before running the assertion

Change-Id: Ibc357094d97717f8f6f53d82c65c5107d5a8c438
Reviewed-on: http://review.couchbase.org/76978
Tested-by: Mark Nunberg <dab05a0fe859c5cb93882b2a75a0d613501b07be@couchbase.com>
Reviewed-by: Subhashni Balakrishnan <7129c8e37b832c7bd362ff375532d24b98ef5162@gmail.com>

couchbase/couchbase-python-client,couchbase/couchbase-python-client