kubelet: revamp the pod/container naming scheme

There are two main goals for this change.

 1. Fix the naming scheme in kubelet so that it accepts DNS subdomain
    name/namespaces correctly (#4920). The design is discussed in #3453.

 2. Prepare for syncing the static pods back to the apiserver(#4090). This
    includes

  - Eliminate the source component in the internal full pod name (#4922). Pods
    no longer need sources as they will all be sync'd via apiserver.

  - Changing the naming scheme for the static (file-, http-, and etcd-based)
    pods such that they are distinguishable when syncing back to the apiserver.

The changes includes:
  *	name = <pod.Name>-<hostname>
  * namespace = <cluster_namespace> (i.e. "default" for now).
  * container_name = k8s_<contianer_name>.<hash_of_container>_<pod_name>_<namespace>_<uid>_<random>

Note that this is not backward-compatible, meaning the kubelet won't recognize
existing running containers using the old naming scheme.

pkg/kubelet/types.go

@@ -50,6 +50,8 @@ const (
 	ApiserverSource = "api"
 	// Updates from all sources
 	AllSource = "*"
+
+	NamespaceDefault = api.NamespaceDefault
 )
 
 // PodUpdate defines an operation sent on the channel. You can add or remove single services by
@@ -69,5 +71,12 @@ type PodUpdate struct {
 
 // GetPodFullName returns a name that uniquely identifies a pod across all config sources.
 func GetPodFullName(pod *api.BoundPod) string {
-	return fmt.Sprintf("%s.%s.%s", pod.Name, pod.Namespace, pod.Annotations[ConfigSourceAnnotationKey])
+	// Use underscore as the delimiter because it is not allowed in pod name
+	// (DNS subdomain format), while allowed in the container name format.
+	return fmt.Sprintf("%s_%s", pod.Name, pod.Namespace)
+}
+
+// Build the pod full name from pod name and namespace.
+func BuildPodFullName(name, namespace string) string {
+	return name + "_" + namespace
 }