ansible generated inventory: skip group variables

Except ':children' for groups of groups, it is safer to avoid generating
':suffix' blocks. At the moment Ansible only supports (but doesn't
recommend) group variables (:vars), and the Vagrant Ansible provisioner
won't support this way to define variables.

plugins/provisioners/ansible/provisioner.rb

@@ -110,7 +110,8 @@ module VagrantPlugins
 
             if gname.end_with?(":children")
               groups_of_groups[gname] = gmembers
-            else
+            elsif !gname.include?(':')
+              # skip group variables [:vars] and any other ":" suffixes
               included_groups << gname
               file.write("\n[#{gname}]\n")
               gmembers.each do |gm|