ipa-rmkeytab: convert numeric return values to #defines
    
    This makes it clearer what the return value means.
    
    Replace closing of keytab based on the numeric return value
    and do it based on whether the keytab was opened at all.
    
    https://pagure.io/freeipa/issue/8658
    
    Signed-off-by: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>