test_driver: Fix permissions for test_driver.c

Introduced in commit 4a6ee535.
Signed-off-by: NAndrea Bolognani <abologna@redhat.com>
(cherry picked from commit df1b5cf0)

Reintroduced-by: fb275b76Signed-off-by: NJán Tomko <jtomko@redhat.com>