MB-3591 Fix to the performance issue on incremental backup client.
MB-3591 Fix to the performance issue on incremental backup client.

We observed that the incremental backup client is quite slow
even if it runs on the local host because it currently does
a commit for every update operation. This change fixes this issue
by performing a single commit for every N updates where N is a
configurable parameter.

Change-Id: I3a9f87741ea687c9583bf5c5fab01fd5272f6fb5
Reviewed-on: http://review.membase.org/5332
Tested-by: Chiyoung Seo <8b279095f11c26cc21045fda5a3e51debb005aa9@gmail.com>
Reviewed-by: Bin Cui <ed18693fff32c00e22495f4877a3b901bed09041@gmail.com>

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