Add nc to the packages to install during upgrade

Upgrade uses nc, but doesn't enforce its presence.
This makes sure nc is installed.

On top of it, the filenames used are ubuntu ones,
so this moves to use a var to find which filename
should be used for centos.

See also the issue here:
http://logs.openstack.org/periodic/periodic-openstack-ansible-
upgrade-ceph-master-centos-7/d2fc540/
console.html#_2017-05-30_08_23_40_475244

Change-Id: I3ee2dfd6e435fb4d92a57e2debf7f001f7c03f98

scripts/upgrade-utilities/playbooks/memcached-flush.yml

@@ -15,9 +15,17 @@
 
 - name: Memcached cache flush
   hosts: memcached_all
-  gather_facts: false
+  gather_facts: true
   user: root
+  vars:
+    memcached_conf_dest:
+      debian: "/etc/memcached.conf"
+      redhat: "/etc/sysconfig/memcached"
   tasks:
+    - name: Ensuring nc is installed
+      package:
+        name: nc
+        state: present
     - name: Flush all of the cache in memcached
       shell: |
-        echo 'flush_all' | nc $(awk '/^\-l/ {print $2}' /etc/memcached.conf | awk -F, '{ print $1 }') $(awk '/^\-p/ {print $2}' /etc/memcached.conf)
+        echo 'flush_all' | nc $(awk '/^\-l/ {print $2}' {{ memcached_conf_dest.get(ansible_os_family | lower) }} | awk -F, '{ print $1 }') $(awk '/^\-p/ {print $2}' {{ memcached_conf_dest.get(ansible_family | lower) }} )