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/runonce_test.go

@@ -76,7 +76,7 @@ func TestRunOnce(t *testing.T) {
 	}
 	podContainers := []docker.APIContainers{
 		{
-			Names:  []string{"/k8s_bar." + strconv.FormatUint(dockertools.HashContainer(&api.Container{Name: "bar"}), 16) + "_foo.new.test_12345678_42"},
+			Names:  []string{"/k8s_bar." + strconv.FormatUint(dockertools.HashContainer(&api.Container{Name: "bar"}), 16) + "_foo_new_12345678_42"},
 			ID:     "1234",
 			Status: "running",
 		},
@@ -130,10 +130,9 @@ func TestRunOnce(t *testing.T) {
 	results, err := kb.runOnce([]api.BoundPod{
 		{
 			ObjectMeta: api.ObjectMeta{
-				UID:         "12345678",
-				Name:        "foo",
-				Namespace:   "new",
-				Annotations: map[string]string{ConfigSourceAnnotationKey: "test"},
+				UID:       "12345678",
+				Name:      "foo",
+				Namespace: "new",
 			},
 			Spec: api.PodSpec{
 				Containers: []api.Container{