Pressing back button in game would not stop the jetpack sound. This commit adds code at Line 458 and 508 where the back button goes to the main menu now stops the jetpack sound from playing.

Steps to reproduce the bug (before this commit):
1.	Play a single player game.
2.	Hold down left trigger to jetpack around.
3.	Press back button while left trigger/left button is pressed.
4.	The menu is displayed. The jetpack sound continues to play.