Fixes Cordova error when trying to open the app from the notification bar

The application is not launching when selecting the notification in the notification bar. This is what Cordova prints on the error log:

```
D/Cordova(5807): This isn't the root activity. Clearing it and returning to the root activity.
```

This happens because Cordova expects the main activity to be the root activity. In this case, the root activity is a PushHandlerActivity instance.

The error can be solved finishing the PushHandlerActivity before sending the intent to launch the main activity.