Add script to make ansible groups from patterns

We have a set of hostname patterns which is not a thing that ansible
supports in inventory files. While we can put hostname patterns into
playbooks directly, that does not help us with copying hiera group files
since ansible doesn't know about the groups in site.pp and puppet
doesn't know about the ansible groups.

Instead, do a quick expansion any time the groups.txt file changes and
at the end of launch-node. It will be left to admins to run
expand-groups.sh whenever they delete a node.

Change-Id: I00c60748ddb2d35a3b98f78d828dabebcf065118

launch/launch-node.py

@@ -300,6 +300,7 @@ def main():
     # server
     if os.path.exists('/var/cache/ansible-inventory/ansible-inventory.cache'):
         os.unlink('/var/cache/ansible-inventory/ansible-inventory.cache')
+    os.system('/usr/local/bin/expand-groups.sh')
 
 if __name__ == '__main__':
     main()