Alt+tab fix for rP22314 - call sound IdleTask in Atlas and swap buffers only once in Atlas.
- rP22314 moved SwapBuffers inside Render - this makes Atlas call it twice in a row which might behave oddly (did not seem to though) and anyways was wasteful.
- rP22314 moved IdleTask from the sound manager outside of Render. This means atlas never called IdleTask, and this broke sounds after a few seconds.
Reviewed By: Angen
Differential Revision: https://code.wildfiregames.com/D2029