Fix memory leak in engine_testapp when destroying cookie
Fix memory leak in engine_testapp when destroying cookie

We need to decrement the reference counter when we are done with a
cookie otherwise it won't actually be freed.

Change-Id: I35cc19f36a50a61e4be8f9701972c75695313fb3
Reviewed-on: http://review.couchbase.org/37977
Reviewed-by: Chiyoung Seo <fcffc23db27b19ee4ebba46695ee6b50e09216a2@couchbase.com>
Tested-by: Michael Wiederhold <a17fed27eaa842282862ff7c1b9c8395a26ac320@couchbase.com>

couchbase/memcached,couchbase/memcached,jimwwalker/memcached,owendCB/memcached,daverigby/kv_engine,daverigby/kv_engine,owendCB/memcached,cloudrain21/memcached-1,daverigby/kv_engine,mrkwse/memcached,jimwwalker/memcached,owendCB/memcached,couchbase/memcached,daverigby/kv_engine,cloudrain21/memcached-1,mrkwse/memcached,daverigby/memcached,daverigby/memcached,daverigby/memcached,mrkwse/memcached,owendCB/memcached,daverigby/memcached,cloudrain21/memcached-1,cloudrain21/memcached-1,jimwwalker/memcached,mrkwse/memcached,couchbase/memcached