containerd-stress: add snapshotter option for stress test to use

containerd-stress utility needs to be able to run with snapshotter
passed by user in cli in order to be able to stress test snapshotters.
This adds a cli option --snapshotter="<snapshotter-name>"

Signed-off-by: Alakesh Haloi <alakeshh@amazon.com>

cmd/containerd-stress/exec_worker.go

@@ -42,6 +42,7 @@ func (w *execWorker) exec(ctx, tctx context.Context) {
 	id := fmt.Sprintf("exec-container-%d", w.id)
 	c, err := w.client.NewContainer(ctx, id,
 		containerd.WithNewSnapshot(id, w.image),
+		containerd.WithSnapshotter(w.snapshotter),
 		containerd.WithNewSpec(oci.WithImageConfig(w.image), oci.WithUsername("games"), oci.WithProcessArgs("sleep", "30d")),
 	)
 	if err != nil {