This reverts commit d678fa56d1. The
reference counter, flawed as it is, was masking far more issues than I
realized. It would require a more significant rearchitecture of the
code to remove it. Probably better to keep it and try to improve it for
now.
This was an old attempt at gracefully unloading channels that still had
pending callbacks. Its implementation was always flawed, and the number
of places where it was used is small enough to replace with
straightforward checks for whether the channel has been unloaded after
an asynchronous operation. Hopefully fixes the stuck 0 user channels
issue.
