ad: set min and max ssf for ldaps
    
    AD does not allow to use encryption in the TLS and SASL layer at the
    same time. To be able to use ldaps this patch sets min and max ssf to 0
    if ldaps should be used.
    
    Related to https://pagure.io/SSSD/sssd/issue/4131
    
    Reviewed-by: Pavel Březina <pbrezina@redhat.com>