Editor delay on end simulation in 4.14

When stopping PIE Selected Viewport or Simulate Mode there is now a 1 to 2 second delay that did not occur in previous versions of the Engine.

Regression: Did not occur in UE4.13 or earlier

1. Open a Blank Blueprint Project in UE4.14
2. PIE Selected Viewport or Simulate
3. Stop
   RESULT: Delayed 1 to 2 seconds before returning to editor mode
   EXPECTED: To return to editor mode immediately as in previous versions of the Engine

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