test: Maintain a list of activated players for automated cleanup

test: Maintain a list of activated players for automated cleanup

The list of deactivate calls at the end of the test sutie was getting
rather messy, (since it required awareness of which players had been
activated in specific tests and then also which had _not_ been
deactivated in other tests).

Instead, we now store an array of each activated player, and loop over
that deactivating all players at the end. We also make deactivate
idempotent, safely doing nothing if we ask to deactivate a plyer which
was already deactivated.