shmem: add anon shmem dumping to predump command

As anon shmem dumping supports page changes tracking
we can call it during predump.
Signed-off-by: Eugene Batalov <eabatalov89@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/cr-dump.c

@@ -1541,6 +1541,10 @@ int cr_pre_dump_tasks(pid_t pid)
 		if (pre_dump_one_task(item))
 			goto err;
 
+	ret = cr_dump_shmem();
+	if (ret)
+		goto err;
+
 	if (irmap_predump_prep())
 		goto err;