MB-5138 Return the value size as 0 for partially loaded items.
MB-5138 Return the value size as 0 for partially loaded items.

Change-Id: I723ee5823c9772c00eae921dc1843e4e78de2229
Reviewed-on: http://review.couchbase.org/15215
Reviewed-by: Jin Lim <c45cd80a556f432a3607171a6818cd5a074b5cd4@couchbase.com>
Tested-by: Jin Lim <c45cd80a556f432a3607171a6818cd5a074b5cd4@couchbase.com>

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