Properly handle unresolved promises in training script

[taylorhansen]

If something happens where both sides of the Battle have not sent any messages to the BattleStream and are instead waiting to read from it, this causes the Promise.all statement in the play() function to never resolve, causing an immediate termination of the process. Either figure out a way to detect and handle this, or just cover all corner cases where this may happen. Doing both would be preferable here.

[taylorhansen]

This looks promising.

[taylorhansen]

After looking at some of the recent training script changes, I think this is resolved now.