vars: Add missing netcat package

Commit afc0e5b1ce66 ("Add memcache flushing handler on db migrations")
added an implicit dependency to the 'nc' package but it did not add it
to the list of required packages so things break like this:

 ["/bin/sh: nc: command not found"]

As such, we need to add the package to the rest of the distro packages.

Fixes: afc0e5b1ce66 ("Add memcache flushing handler on db migrations")
Change-Id: Ieab35215e84d6971cd9c2068206ebf2103cbc4b4

vars/redhat-7.yml

@@ -18,6 +18,7 @@ keystone_distro_packages:
   - cronie
   - cronie-anacron
   - git
+  - nc
   - openssh-server
   - rsync
 

vars/suse.yml

@@ -18,6 +18,7 @@ keystone_distro_packages:
   - ca-certificates
   - cronie
   - git-core
+  - netcat-openbsd
   - openssh
   - rsync
 

vars/ubuntu.yml

@@ -17,6 +17,7 @@ cache_timeout: 600
 
 keystone_distro_packages:
   - git
+  - netcat
   - openssh-server
   - rsync