Graph: Fixed graph tooltip getting stuck / not being cleared when leaving dashboard, fixes #23881 (#24162)

(cherry picked from commit f273e56adc)

public/app/features/dashboard/state/PanelModel.ts

@@ -467,6 +467,7 @@ export class PanelModel implements DataConfigSource {
   }
 
   destroy() {
+    this.events.emit(PanelEvents.panelTeardown);
     this.events.removeAllListeners();
 
     if (this.queryRunner) {

public/app/features/panel/panel_directive.ts

@@ -82,9 +82,6 @@ module.directive('grafanaPanel', ($rootScope, $document, $timeout) => {
       scope.$on('$destroy', () => {
         elem.off();
 
-        panel.events.emit(PanelEvents.panelTeardown);
-        panel.events.removeAllListeners();
-
         if (panelScrollbar) {
           panelScrollbar.dispose();
         }