MB-19029: Wait for consumer task to run before checking backoffs
MB-19029: Wait for consumer task to run before checking backoffs

Backfoff stat is updated only after consumer processor task runs. Hence it
is better to wait for the stat than to query it for a particular value.

Change-Id: I8c88f76d5ac6d6623ae5b3681438a3dd6c05ea65
Reviewed-on: http://review.couchbase.org/62808
Reviewed-by: Dave Rigby <a09264da4832c7ff1d3bf1608a19f4b870f93750@couchbase.com>
Reviewed-by: Chiyoung Seo <fcffc23db27b19ee4ebba46695ee6b50e09216a2@couchbase.com>
Tested-by: Manu Dhundi <158873d90a7ef40f3637a222b7329c09d0222554@couchbase.com>

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