Improve user addition to default group in user-add
    
    On adding new user, user-add tries to make it a member of default
    user group. This, however, can raise AlreadyGroupMember when the
    user is already member of this group due to automember rule or
    default group configured. This patch makes sure AlreadyGroupMember
    exception is caught in such cases.
    
    https://fedorahosted.org/freeipa/ticket/3097