Update path to allow commit validation for libmemcached

Change-Id: I02a937e83dd848e513d861336b5fda710d81adb8
Reviewed-on: http://review.couchbase.org/38492
Reviewed-by: Eric Limare <eric.limare@couchbase.com>
Tested-by: Eric Limare <eric.limare@couchbase.com>