renew agent: revert to host keytab authentication
    
    Fixes an issue where the renew agent uses GSSAPI for LDAP connection but
    fails because it is not authenticated.
    
    This reverts commit 7462adec13c5b25b6868d2863dc38062c97d0ff7.
    
    https://pagure.io/freeipa/issue/6757
    
    Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>