CBQE-1489: add test: kill memcached and it recovers

Change-Id: I5d3943b587862080950378b23529d88b791cdc2f
Reviewed-on: http://review.couchbase.org/37175
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: buildbot <build@couchbase.com>