Add blank /stats/summary kubelet endpoint

Add a `/stats/summary` endpoint to the kubelet which will return an
empty Summary{} struct (json formatted), as a summary API
placeholder. Once the next cAdvisor release is vendored, the summary
API will be filled in.

pkg/kubelet/server/stats/handler.go

@@ -56,6 +56,7 @@ func CreateHandlers(provider StatsProvider) *restful.WebService {
 		handler restful.RouteFunction
 	}{
 		{"", h.handleStats},
+		{"/summary", h.handleSummary},
 		{"/container", h.handleSystemContainer},
 		{"/{podName}/{containerName}", h.handlePodContainer},
 		{"/{namespace}/{podName}/{uid}/{containerName}", h.handlePodContainer},
@@ -134,6 +135,15 @@ func (h *handler) handleStats(request *restful.Request, response *restful.Respon
 	writeResponse(response, statsMap["/"])
 }
 
+// Handles stats summary requests to /stats/summary
+func (h *handler) handleSummary(request *restful.Request, response *restful.Response) {
+	summary := Summary{}
+
+	// TODO(timstclair): Fill in summary from cAdvisor v2 endpoint.
+
+	writeResponse(response, summary)
+}
+
 // Handles non-kubernetes container stats requests to /stats/container/
 func (h *handler) handleSystemContainer(request *restful.Request, response *restful.Response) {
 	query, err := parseStatsRequest(request)