restore: fix --manage-cgroups-mode ignore on cgroup v2

When manage-cgroups-mode: ignore is used, criu still needs to know the
cgroup path to work properly (see [1]).

Revert "libct/criuApplyCgroups: don't set cgroup paths for v2"

This reverts commit d5c57dc.

[1]: checkpoint-restore/criu#1793 (comment)

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

libcontainer/container_linux.go

@@ -1560,11 +1560,6 @@ func (c *Container) criuApplyCgroups(pid int, req *criurpc.CriuReq) error {
 		return err
 	}
 
-	if cgroups.IsCgroup2UnifiedMode() {
-		return nil
-	}
-	// the stuff below is cgroupv1-specific
-
 	path := fmt.Sprintf("/proc/%d/cgroup", pid)
 	cgroupsPaths, err := cgroups.ParseCgroupFile(path)
 	if err != nil {