LDAP: save non-POSIX users in application domains
    
    Related to:
    https://pagure.io/SSSD/sssd/issue/3310
    
    If a user being saved by the LDAP provider does not have a UID or GID
    and the domain type is application, we save the user entry as non-POSIX.
    
    Reviewed-by: Sumit Bose <sbose@redhat.com>