[CBD-1191]: Change permission to libmemcached-gerrit.sh

Change-Id: Id755f646aea04dff2c5fb88f0b33ba8b8ab6e617
Reviewed-on: http://review.couchbase.org/34348
Reviewed-by: Eric Limare <eric.limare@couchbase.com>
Tested-by: Eric Limare <eric.limare@couchbase.com>