assert if mock file remove fails. Use env for test dir
assert if mock file remove fails. Use env for test dir

Change-Id: I88640746259cd7d954d07e7d760deb1dc504272b
Reviewed-on: http://review.couchbase.org/39981
Tested-by: Sundararaman Sridharan <333a3f71d3ad6e01fc953c4fa06bc1f3cd014910@couchbase.com>
Reviewed-by: Michael Wiederhold <a17fed27eaa842282862ff7c1b9c8395a26ac320@couchbase.com>

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