PTR on a page doesn't update the page contents

How to reproduce:

1. Open a page in the app.
2. In web as teacher, edit the page contents.
3. In the app, perform a PTR. Check that the page contents aren't updated.

We aren't checking if the module has updates at the beginning of downloadResourceIfNeeded, so the app detects that the page hasn't changed and it doesn't download the file again. However, fixing this isn't trivial because:

• We also need to invalidate the check updates WS call.
• Currently getModuleStatus gets the updates of the whole course, and I'm not sure if we want that. We could probably use getModuleUpdates, but that doesn't change the status of the package.
• When the refresh is done we call fillContextMenu that calls getModuleStatus again. It should use cached data, but still we're calling a function when it probably isn't needed.