ipa-client-automount: Don't use deprecated ipadiscovery.IPADiscovery
    
    This class was moved to ipaclient/discovery.py in e6d560af66 to make
    it available to PyPI.
    
    Related: https://pagure.io/freeipa/issue/9487
    
    Signed-off-by: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>