automount install: fix checking of SSSD functionality on uninstall
    
    Change in 2d4d1a9dc0ef2bbe86751768d6e6b009a52c0dc9 no longer initializes
    api in `ipa-client-automount --uninstallation` Which caused error in
    wait_for_sssd which gets realm from initialized API.
    
    This patch initializes the API in a way that it doesn't download schema
    on uninstallation and on installation it uses host keytab for it so it
    no longer requires user's Kerberos credentials.
    
    Also fix call of xxx_service_class_factory which requires api as param.
    
    https://pagure.io/freeipa/issue/6861
    
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Tomas Krizek <tkrizek@redhat.com>