Prevent start of combat sound alert from overrunning other combat sounds

[cswendrowski]

Currently, start of combat alerts will play alongside alerts for your turn and next turn (as appropriate to the user), which does not sound good. The tracker should probably play sounds one after another for a user, and wait for the first sound to finish playing before starting the next one.

alternatively, the tracker can simply prioritize the combat start sound over all others on the first round, and then resume normal alerting as the combat round progresses.