Free engine event callbacks on shutdown
Free engine event callbacks on shutdown

Free any allocated engine event callbacks when shutting down
memcached. No actual leak here, but gives a cleaner Valgrind result to
ensure we spot 'real' leaks.

Change-Id: I8d7a804727794d5c2dd5db17784153478974c10f
Reviewed-on: http://review.couchbase.org/52624
Tested-by: Dave Rigby <a09264da4832c7ff1d3bf1608a19f4b870f93750@couchbase.com>
Reviewed-by: Jim Walker <1cd02e31b43620d7c664e038ca42a060d61727b9@couchbase.com>
Reviewed-by: Trond Norbye <60edd2ef23891a753f231b0c6f161dc634079a93@gmail.com>

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