Refactor Kubelet config sources for clarity

Create a new "Pod" concept which can identify pods from
many config sources.

pkg/tools/etcd_tools.go

@@ -70,6 +70,11 @@ func IsEtcdConflict(err error) bool {
 	return isEtcdErrorNum(err, 101)
 }
 
+// IsEtcdWatchStoppedByUser returns true iff err is a client triggered stop.
+func IsEtcdWatchStoppedByUser(err error) bool {
+	return etcd.ErrWatchStoppedByUser == err
+}
+
 // Returns true iff err is an etcd error, whose errorCode matches errorCode
 func isEtcdErrorNum(err error, errorCode int) bool {
 	etcdError, ok := err.(*etcd.EtcdError)

pkg/tools/fake_etcd_client.go

@@ -124,6 +124,10 @@ func (f *FakeEtcdClient) Watch(prefix string, waitIndex uint64, recursive bool,
 	defer close(injectedError)
 	f.WatchInjectError = injectedError
 
+	if receiver == nil {
+		return f.Get(prefix, false, recursive)
+	}
+
 	f.watchCompletedChan <- true
 	select {
 	case <-stop: