SSSDConfig: Port missing parts to python3
    
    * fix incompatible imports
    * fix translation.[u]?gettext
    * fix dict method has_key
    * fix octal literals PEP 3127
    * long is not defined in python3
    
    Resolves:
    https://fedorahosted.org/sssd/ticket/2017
    
    Reviewed-by: Petr Viktorin <pviktori@redhat.com>
    (cherry picked from commit a71004c112cd5d61d3a9e37a4cfc5760dc9a1cec)