session-vnc: Avoid depracated warnings on this file
    
    This is a temporary solution for using autobuild.sh, as commit df403f5
    introduced the -Wdeprecated-declarations and gtk-vnc provides a callback
    for getting authentication credentials which uses GValueArray, forcing
    virt-viewer to keep using g_value_array_get_nth(), which is deprecated.
    
    Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
    Acked-by: Pavel Grunt <pgrunt@redhat.com>