Add context and client to SpecOpts

In order to do more advanced spec generation with images, snapshots,
etc, we need to inject the context and client into the spec generation
code.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

cmd/containerd-stress/main.go

@@ -98,7 +98,7 @@ func test(c config) error {
 		return err
 	}
 	logrus.Info("generating spec from image")
-	spec, err := containerd.GenerateSpec(containerd.WithImageConfig(ctx, image), containerd.WithProcessArgs("true"))
+	spec, err := containerd.GenerateSpec(ctx, client, containerd.WithImageConfig(image), containerd.WithProcessArgs("true"))
 	if err != nil {
 		return err
 	}