fix(router): fix issue 16710

Fix issue 16710. Navigation events are called twice when using HashLocationStrategy. When user change url manually in browser URL.
ex: Router A(component A) using navigateByUrl(in guard) to redirect to Router B(Component B). When user enter router A in browser URL. That follow will be call twice. Detail in issue 16710

angular#16710

packages/router/src/router.ts

@@ -1075,6 +1075,10 @@ export class Router {
         lastNavigation.rawUrl.toString() === rawUrl.toString()) {
       return Promise.resolve(true);  // return value is not used
     }
+    // Fix issue 16710 (https://github.com/angular/angular/issues/16710)
+    if (source !== 'imperative' && this.location.path(true) !== rawUrl.toString()) {
+      return Promise.resolve(true);  // return value is not used
+    }
 
     let resolve: any = null;
     let reject: any = null;