fix compiler warning with forest-kvstore
fix compiler warning with forest-kvstore

Change-Id: I92bd3ca768eaf2857990ed9d600a664ebcc5613b
Reviewed-on: http://review.couchbase.org/64694
Reviewed-by: Sriram Ganesan <fde85c3124eed34938bb85159f430bf7e5b650f6@couchbase.com>
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>

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