cgroup: don't do cgroup moves async

We rely on the synchronous-ness of the behavior because we assume that the
task is in all the right cgroups when forking its children. If it's not,
and the child has the same cgroups as its parent but not all the moves are
done, it might end up in /.
Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/cgroup.c

@@ -1041,7 +1041,7 @@ static int move_in_cgroup(CgSetEntry *se)
 			pr_info("setting cgns prefix to %s\n", ce->path);
 			snprintf(aux + aux_off, sizeof(aux) - aux_off, "/%s/tasks", ce->path);
 			ce->path[ce->cgns_prefix] = tmp;
-			if (userns_call(userns_move, UNS_ASYNC, aux, strlen(aux) + 1, -1) < 0) {
+			if (userns_call(userns_move, 0, aux, strlen(aux) + 1, -1) < 0) {
 				pr_perror("couldn't set cgns prefix %s", aux);
 				return -1;
 			}
@@ -1060,7 +1060,7 @@ static int move_in_cgroup(CgSetEntry *se)
 		 */
 		snprintf(aux + aux_off, sizeof(aux) - aux_off, "/%s/tasks", ce->path);
 		pr_debug("  `-> %s\n", aux);
-		err = userns_call(userns_move, UNS_ASYNC, aux, strlen(aux) + 1, -1);
+		err = userns_call(userns_move, 0, aux, strlen(aux) + 1, -1);
 		if (err < 0) {
 			pr_perror("Can't move into %s (%d/%d)", aux, err, fd);
 			return -1;