LDAP: Relax search filters in application domains
    
    Related to:
    https://pagure.io/SSSD/sssd/issue/3310
    
    If a request comes towards an application domain, we can drop the part
    of the filter that asserts that the object has a valid UID/GID. Instead,
    we just search by name.
    
    Reviewed-by: Sumit Bose <sbose@redhat.com>