bufferpool: Deactivate pool and get rid of references to other objects from...
bufferpool: Deactivate pool and get rid of references to other objects from dispose instead of finalize
During dispose the pool will still have a reference count of 1 and all API on it can still be safely called.
Subclasses will have already freed their own data before finalize is called but would nonetheless be called into again via the pool deactivation.
CC @cmeissl