winrt: Continuous focus does not always work

Precondition: Windows phone that supports continuous focus

Steps:
1. Run attached QML.
2. Move camera close to object
Expected: Camera would focus
Actual: Nothing happens

Steps:
1. Run attached QML.
2. Press "Auto" button
Expected: Focus moved to "Auto" button
Actual: Camera focus mode changed but no change signal fired.

3. Press "Continuous" button
Expected: Focus moved to "Continuous" button
Actual: Focus moved to "Auto" button and continuous focus started working.

Camera reports focusMode out of sync and continuous focus does not always work out of the box on winrt.

Continuous focus:
Lumia 630 - working
Lumia 1520 - not working