Fix validation of ipa-restore options
    
    Fix restore mode checks. Do some of the existing checks earlier to make them
    effective. Check if --instance and --backend exist both in the filesystem and
    in the backup.
    
    Log backup type and restore mode before performing restore.
    
    Update ipa-restore man page.
    
    https://fedorahosted.org/freeipa/ticket/4797
    
    Reviewed-By: Petr Vobornik <pvoborni@redhat.com>
    Reviewed-By: Martin Kosek <mkosek@redhat.com>