Make CouchKVStore::getMultiCb use the context's kvstore's logger
Make CouchKVStore::getMultiCb use the context's kvstore's logger

This is intended to make it possible to verify the logging output
in the callback by using the same injected logger as the
CouchKVStore.

Change-Id: Ib0eafe19e8c5d27b5c4dae99b3762b95e152aaef
Reviewed-on: http://review.couchbase.org/62563
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Dave Rigby <a09264da4832c7ff1d3bf1608a19f4b870f93750@couchbase.com>
Reviewed-by: Chiyoung Seo <fcffc23db27b19ee4ebba46695ee6b50e09216a2@couchbase.com>

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