MB-16434: In setDead release streamMutex before cleaning up stream buffer
MB-16434: In setDead release streamMutex before cleaning up stream buffer

To avoid lock order inversion in DCP passive stream we must release streamMutex
before acquiring bufMutex. This is because while processing incoming mutations
on dcp consumer we acquire bufMutex first and then streamMutex.

Change-Id: I129d014dc3a7ec91416af04851419782b89cea23
Reviewed-on: http://review.couchbase.org/55707
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Chiyoung Seo <fcffc23db27b19ee4ebba46695ee6b50e09216a2@couchbase.com>

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