VR preview does not work when the project was converted from 4.7 to 4.8

If the user upgrade a project form 4.7 to 4.8 the VR preview will only show up as a regular stand alone window.

1. Create a 4.7 project
2. Save
3. Open up that same project in 4.8
4. Make sure that the oculus is plugged in and turned on
5. Click the VR preview button
6. Notice that the window that comes up does not show up in VR mode (no stereo)

[4.8] VR preview sometimes doesn't work, bad GPU-utilisation

[4.8] VR preview sometimes doesn't work, bad GPU-utilisation

VR Preview not working when Blueprint is open

[4.8] VR preview sometimes doesn't work, bad GPU-utilisation