Merge pull request #716 from edx/feanil/move_common_variants

Add the common variants so that package logic can use the where necessar...

playbooks/roles/common/defaults/main.yml

@@ -49,3 +49,11 @@ common_git_ppa: "ppa:git-core/ppa"
 # Skip supervisor tasks
 # Useful when supervisor is not installed (local dev)
 devstack: False
+
+common_debian_variants:
+  - Ubuntu
+  - Debian
+
+common_redhat_variants:
+  - CentOS
+  - Red Hat Enterprise Linux