Better kubelet logging for probes

Log when we actually run probes and event when they fail.  Print the output of
a probe, too.

cmd/integration/integration.go

@@ -81,8 +81,8 @@ func (fakeKubeletClient) GetConnectionInfo(host string) (string, uint, http.Roun
 	return "", 0, nil, errors.New("Not Implemented")
 }
 
-func (fakeKubeletClient) HealthCheck(host string) (probe.Result, error) {
-	return probe.Success, nil
+func (fakeKubeletClient) HealthCheck(host string) (probe.Result, string, error) {
+	return probe.Success, "", nil
 }
 
 type delegateHandler struct {