Reset the use_count to zero in chan_free

It is possible that the BTS is closing the channel even when
our upper layers are doing work. Reset the use_count add a fixme
to call cancellations for pending operations. Cancellation of the
call state (state machines in general) and such come into mind...

tree: 5562f8e489233fc4d95776920a1ab3c80b7dacf2
  1. tests/
  2. tools/
  3. AUTHORS
  4. configure.in
  5. COPYING
  6. Makefile.am
  7. README