Use 'fe' instead of 'frontend'

There is some preference for using shorter host names so make
git-frontendXX git-feXX instead.

Change-Id: I8a5d80b3f0df537890abd18a22e62a22bc19c51f

manifests/site.pp

@@ -361,7 +361,7 @@ node /^elasticsearch0[1-7]\.openstack\.org$/ {
 
 # CentOS machines to load balance git access.
 # Node-OS: centos6
-node /^git(-frontend\d+)?\.openstack\.org$/ {
+node /^git(-fe\d+)?\.openstack\.org$/ {
   class { 'openstack_project::git':
     sysadmins               => hiera('sysadmins', []),
     balancer_member_names   => [