getContainerGroups(person) gets the groups that contain the
      specified authority.
    Parameters
- person
- The user (cm:person) to get the containing groups for.
Example
The following code returns a list of groups that abeecher is a member of:
var user = people.getPerson("abeecher");
if(user){
    model.containers = people.getContainerGroups(user);
}
    