Don't emit 0 histo values.
Don't emit 0 histo values.

Change-Id: Icfa034ab8e2627caa7848fb5c1adf0700c4a1d65
Reviewed-on: http://review.northscale.com/2984
Tested-by: Chiyoung Seo <8b279095f11c26cc21045fda5a3e51debb005aa9@gmail.com>
Reviewed-by: Chiyoung Seo <8b279095f11c26cc21045fda5a3e51debb005aa9@gmail.com>

zbase/ep-engine,daverigby/ep-engine,couchbase/ep-engine,sriganes/ep-engine,sriganes/ep-engine,couchbaselabs/ep-engine,sriganes/ep-engine,daverigby/ep-engine,daverigby/kv_engine,teligent-ru/ep-engine,zbase/ep-engine,teligent-ru/ep-engine,teligent-ru/ep-engine,abhinavdangeti/ep-engine,jimwwalker/ep-engine,membase/ep-engine,hisundar/ep-engine,couchbase/ep-engine,couchbaselabs/ep-engine,jimwwalker/ep-engine,owendCB/ep-engine,membase/ep-engine,couchbaselabs/ep-engine,membase/ep-engine,membase/ep-engine,daverigby/kv_engine,zbase/ep-engine,couchbaselabs/ep-engine,hisundar/ep-engine,daverigby/kv_engine,abhinavdangeti/ep-engine,jimwwalker/ep-engine,daverigby/kv_engine,abhinavdangeti/ep-engine,couchbase/ep-engine,daverigby/ep-engine,zbase/ep-engine,abhinavdangeti/ep-engine,abhinavdangeti/ep-engine,hisundar/ep-engine,hisundar/ep-engine,couchbase/ep-engine,daverigby/ep-engine,sriganes/ep-engine,owendCB/ep-engine,zbase/ep-engine,jimwwalker/ep-engine,couchbaselabs/ep-engine,teligent-ru/ep-engine,owendCB/ep-engine,owendCB/ep-engine