Gamepad continues to control editor menus during Mobile PIE session

When using a Gamepad, there is an issue where input from the controller continues to control editor menus during Mobile PIE session. This issue does not a appear to be a regression.

Versions Tested: Issue occurs on all versions tested
4.16.3 - CL: 3561208
4.17.2 - CL: 3658906
4.18.1 - CL: 3754814

1. Create a new project ( No template or starter content needed)
2. Plug in a USB controller and ensure it moves around and can control the editor menus
3. Launch a mobile PIE session
4. After the game launches move the control sticks of the controller
   Result: The controller affects both the PIE session and the editor
   Expected Result: The controller only affects the PIE session