Restore pipe flags

pipe_loop00 passed with this patch.

When we restore a regular fd (not pipe) we do use flags
directly in open() call.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>