fix(mock): Timer.isActive should be false after running callback
fix(mock): Timer.isActive should be false after running callback

For non-periodic timers, isActive should be false after running the timer function.

https://api.dartlang.org/apidocs/channels/stable/dartdoc-viewer/dart-async.Timer#id_isActive

ronlobo/angular.dart,winstonewert/angular.dart,giovannicandido/angular.dart,rkirov/angular.dart,winstonewert/angular.dart,hitesh97/angular.dart,hitesh97/angular.dart,trinarytree/angular.dart,trinarytree/angular.dart,hitesh97/angular.dart,ronlobo/angular.dart,SibuStephen/angular.dart,SibuStephen/angular.dart,SibuStephen/angular.dart,ronlobo/angular.dart,rkirov/angular.dart,ronlobo/angular.dart,trinarytree/angular.dart,trinarytree/angular.dart,SibuStephen/angular.dart,giovannicandido/angular.dart,rkirov/angular.dart,rkirov/angular.dart,hitesh97/angular.dart,winstonewert/angular.dart,winstonewert/angular.dart,giovannicandido/angular.dart