CLIENT: Fix warning Wstringop-overflow
    
    It could not cause any problem because all strings were
    compile time constants (defines). But it's better to check
    that we have enough data for storing NUL terminated string in
    nssaddr.sun_path
    
    src/sss_client/common.c: In function ‘sss_cli_check_socket’:
    src/sss_client/common.c:544:5: warning: ‘strncpy’ specified bound depends
        on the length of the source argument [-Wstringop-overflow=]
         strncpy(nssaddr.sun_path, socket_name,
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                 strlen(socket_name) + 1);
                 ~~~~~~~~~~~~~~~~~~~~~~~~
    src/sss_client/common.c:545:13: note: length computed here
                 strlen(socket_name) + 1);
                 ^~~~~~~~~~~~~~~~~~~
    
    Reviewed-by: Fabiano Fidêncio <fidencio@redhat.com>
    (cherry picked from commit bd5f48540b25dae81c43feb1d6aba4175da52098)