MB-5908 snapshot vbuckets state in descending order
MB-5908 snapshot vbuckets state in descending order

This simple optimization reduces db file contention between
CouchKVStore and Couchstore Compactor.

Change-Id: I6e8c363e7eba0ffeffab5c70f3a40be82db95115
Reviewed-on: http://review.couchbase.org/18536
Reviewed-by: Chiyoung Seo <8b279095f11c26cc21045fda5a3e51debb005aa9@gmail.com>
Tested-by: Chiyoung Seo <8b279095f11c26cc21045fda5a3e51debb005aa9@gmail.com>

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