fault/vdso/restorer: add force-injection of trampolines

To check that jump trampolines to rt-vdso works.

Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>