Comment 1 for bug 1260838

If the user has passthrough active, and then they try to enable sync mode, should we:
1. disable passthrough, or
2. disallow the enable change?

When vinyl control is active, we disable vinyl control -- this makes sense because we're handing off from vinyl control to sync control. But for passthrough, disabling passthrough would cause a complete change in audio processing. So for now I'm picking 2 and disabling enabling passthrough.

As a protection, if somehow the user forces sync on, I will still disable passthrough. But the idea is to head it off at the pass in synccontrol::slotSyncModeChangeRequest