fixed failing graph tests

public/app/plugins/panel/graph/specs/graph.test.ts

@@ -125,7 +125,7 @@ describe('grafanaGraph', () => {
 
     //Emulate functions called by event listeners
     link.buildFlotPairs(link.data);
-    link.render_panel();
+    link.renderPanel();
     ctx.plotData = ctrl.plot.mock.calls[0][1];
 
     ctx.plotOptions = ctrl.plot.mock.calls[0][2];