users: Leave managed_admin_users' other group memberships alone

users: Leave managed_admin_users' other group memberships alone

This change is mainly so the users role can be run on vps_hosts.

Previously, in order to update the ubuntu user's authorized_keys on
vps_hosts, the testnodes role had to be run which caused ubuntu to be
removed from the libvirtd group.

The ubuntu user is in managed_admin_users on vps_hosts so this will
ensure the user is added to sudo and left in the libvirtd group.

managed_users, on the other hand, we want to make sure are only in
groups we specify so the "Create all users without sudo access." task is
left as-is (without append: yes).

Signed-off-by: David Galloway <dgallowa@redhat.com>