fix conditional for warning while starting KCM without secret file

cmd/kube-controller-manager/app/controllermanager.go

@@ -164,7 +164,7 @@ func Run(s *options.CMServer) error {
 		}
 		var clientBuilder controller.ControllerClientBuilder
 		if s.UseServiceAccountCredentials {
-			if len(s.ServiceAccountKeyFile) > 0 {
+			if len(s.ServiceAccountKeyFile) == 0 {
 				// It's possible another controller process is creating the tokens for us.
 				// If one isn't, we'll timeout and exit when our client builder is unable to create the tokens.
 				glog.Warningf("--use-service-account-credentials was specified without providing a --service-account-private-key-file")