MB-19204: ep_testsuite: Don't release the item while we're using it
MB-19204: ep_testsuite: Don't release the item while we're using it

Fixes a number of issues detected by ThreadSanitizer.

Change-Id: I6ab6c9fee2497d0843af47647f33bcce73111f76
Reviewed-on: http://review.couchbase.org/62909
Well-Formed: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Trond Norbye <60edd2ef23891a753f231b0c6f161dc634079a93@gmail.com>
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Will Gardner <cbd6f5d9092d9ef7d5c0510d53bba134b22c02f2@couchbase.com>

daverigby/kv_engine,daverigby/kv_engine,daverigby/ep-engine,teligent-ru/ep-engine,daverigby/kv_engine,daverigby/kv_engine,membase/ep-engine,membase/ep-engine,teligent-ru/ep-engine,couchbase/ep-engine,daverigby/ep-engine,membase/ep-engine,teligent-ru/ep-engine,teligent-ru/ep-engine,couchbase/ep-engine,membase/ep-engine,daverigby/ep-engine,couchbase/ep-engine,daverigby/ep-engine,couchbase/ep-engine