When checkpoint is done on the kernels where
commit 6933599697c96c3213c95f5f1fc7cb6abfd08c54
is not yet present then mask is not filtered
and saved in image in this raw form.

For such case restore on more modern kernels
will fail because only a small set of events
are allowed to pass from userspace.
Signed-off-by: Cyrill Gorcunov <gorcunov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>