Fix cbstats tasks incorrect key
Fix cbstats tasks incorrect key

Change-Id: I4c2d3551a2b2a3f1ca213bf3cd9b067140f6e67a
Reviewed-on: http://review.couchbase.org/77657
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Dave Rigby <a09264da4832c7ff1d3bf1608a19f4b870f93750@couchbase.com>

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