Cleanup channel callbacks after closing it.
Cleanup channel callbacks after closing it.

Zephor5/pika,jstnlef/pika,hugoxia/pika,fkarb/pika-python3,renshawbay/pika-python3,pika/pika,shinji-s/pika,zixiliuyue/pika,knowsis/pika,skftn/pika,benjamin9999/pika,reddec/pika,vitaly-krugl/pika,vrtsystems/pika,Tarsbot/pika