Pod creation process

1. The user creates a Pod through the REST API
2. The apiserver writes it into etcd
3. The scheduluer detects the Pod that is not bound to the Node, and starts scheduling and updates the Node binding of the Pod.
4. The kubelet detects that a new Pod is scheduled. Run the Pod
through the container runtime 5. kubelet gets the pod status through the container runtime and updates it to the apiserver