FPS drop after highresshot console command

Running the highresshot command with a multiplier of 6 or higher results in poor performance for the remainder of the Editor instance. Closing the PIE window does not improve performance, only closing and relaunching the Editor will bring performance levels back to normal.

1. Create a blank project
2. Launch PIE
3. Open up the console 
   1. Enter Stat FPS
   2. Enter highresshot 6

Results: The framerate is stuck in a very low range and will not catch back up. Closing the PIE window does not make any difference to the FPS counter.

Expected: The framerate should return to normal levels once the high resolution shot has finished.