When fixing mprotected (ro) sysvshmems I used the PROT_EXEC flag
to keep the information about whether the segment itself should
be rw or ro. This flag leaked to sys_mprotect and some attachments
of the segment became executable after restore.

Fix this by dropping the EXEC flag.

https://github.com/xemul/criu/issues/180Reported-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Acked-by: Andrew Vagin <avagin@virtuozzo.com>