Unexpected "delete uploaded file?" dialog

#### Problem description
While testing Annotate widget I noticed a "Delete uploaded file?" dialog after going back to the question without saving a photo on Android.
I took a photo, opened the camera and tapped the device back button to go back to the question.

#### Steps to reproduce the problem
1. Go to All question types form.
2. Go to Annotate widget.
3. Tap "Take picture".
4. Take picture and confirm/save it.
5. Tap "Take picture" again.
6. When the camera is opened tap the device back button.

#### Expected behavior
The dialog shouldn't appear - as I user I didn't intend to remove the photo.

Start by reproducing the flow in the Annotate widget from the All question types form: save a photo, open Take picture again, then use the Android device back button. Trace the camera and back-navigation handling, and verify that backing out of the second camera launch does not show the “Delete uploaded file?” dialog.

Written by the indexing model from the issue text.