Fix closing connection while a channel is still open
Fix closing connection while a channel is still open

Previously, this code would get stuck in a recursive loop trying to send
ChannelClose over a dead connection. This will ensure it tries to send
it at most once before realizing the connection is dead and stopping.

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