Handle streaming serializers more consistently

Add tests to watch behavior in both protocols (http and websocket)
against all 3 media types. Adopt the
`application/vnd.kubernetes.protobuf;stream=watch` media type for the
content that comes back from a watch call so that it can be
distinguished from a Status result.

examples/apiserver/apiserver.go

@@ -94,9 +94,8 @@ func Run(serverOptions *genericapiserver.ServerRunOptions) error {
 		VersionedResourcesStorageMap: map[string]map[string]rest.Storage{
 			groupVersion.Version: restStorageMap,
 		},
-		Scheme:                     api.Scheme,
-		NegotiatedSerializer:       api.Codecs,
-		NegotiatedStreamSerializer: api.StreamCodecs,
+		Scheme:               api.Scheme,
+		NegotiatedSerializer: api.Codecs,
 	}
 	if err := s.InstallAPIGroups([]genericapiserver.APIGroupInfo{apiGroupInfo}); err != nil {
 		return fmt.Errorf("Error in installing API: %v", err)