Mouse Not Being Locked to Viewport in PIE

The mouse cursor is not being locked to the viewport during PIE in versions 4.11 and up.

This is inconsistent with the behavior that was seen in 4.10 because the mouse was locked to the viewport during PIE.

This causes an issue because if you do not notice that your cursor is on the second monitor and you click, the editor will lose focus.

This also seems to occur in Standalone as well.

1. Open the editor (FirstPersonProject)
2. PIE
3. Move the mouse to the right

Result: The mouse cursor will go onto the second monitor

Expected: The mouse would stay locked to the viewport

Mouse Doesn't Stay in Viewport in PIE