The contents of sysvshm areas is sometimes dumped twice.

First time it goes via cr_dump_shmem(), since each attachment
of the segment is noted by the add_shmem_area() and thus
gets into the list scanned by the former call().

Second time it is dumped by dump_ipc_shm_pages().

Another thing is that in the 1st dump memory gets into the
standard pagemap/pages image pair, while in the 2nd time
it's all written as plain byte array into ipcns-shm.img.

At restore contents is read from the ipcns-shm.img (2nd).

While the first way is preferred, let's (temporarily)
eliminate it. Historically these segments were dumped and
restored the 2nd way.
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>