MB-19836:  Correctly set PendingOpsNotifcation task priority
MB-19836:  Correctly set PendingOpsNotifcation task priority

The PendingsOpsNotification task currently has the priority
VBMemoryDeletionPriority (set to 6).  It should have
the priority PendingOpsPriority (set to 0).

Change-Id: I488d8eae7347eb65fe0f8474ae60e939234b972b
Reviewed-on: http://review.couchbase.org/64714
Well-Formed: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Dave Rigby <a09264da4832c7ff1d3bf1608a19f4b870f93750@couchbase.com>
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>

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