Check for connectivity to memcached.

This will attempt to call the daemon's stats command which, if broken, might
hung and cause nrpe to time out.  We want that, as it will give us a clue to
what might be causing some other app to fail.

roles/nagios_client/tasks/main.yml

@@ -31,6 +31,7 @@
   - check_fedmsg_producers_consumers.py
   - check_supybot_plugin
   - check_datanommer_timesince.py
+  - check_memcache_connect
   when: not inventory_hostname.startswith('noc')
   tags:
   - nagios_client