test/driver: Fix for Python 2.6
Fix GLib-CRITICAL message opening empty file with glib < 2.32

On glib < 2.32, calling g_key_file_load_from_data() with length == 0
produces:

    GLib-CRITICAL **: g_key_file_load_from_data: assertion `length != 0' failed
test: Fix some spurious failures on RHEL 6