GPO: Set libsmb debugging to stderr
    
    libsmb logs to stdout by default. It's much more reasonable to log to
    stderr by default.
    
    Please also note:
        https://bugzilla.samba.org/show_bug.cgi?id=11036
    and:
        https://fedorahosted.org/sssd/ticket/2544
    
    Reviewed-by: Sumit Bose <sbose@redhat.com>
    (cherry picked from commit bb7ddd2be9847bfb07395341c7623da1b104b8a6)