[amqp] patched amq-client send_heartbeat(), don't send frames on closed channels
[amqp] patched amq-client send_heartbeat(), don't send frames on closed channels

m4ce/sensu,upfluence/sensu,somic/sensu,solarkennedy/sensu,npe9/sensu,portertech/sensu,pauloconnor/sensu,withnale/sensu,roobert/sensu,sensu/sensu,yonglehou/sensu,rbramwell/sensu,crewton/sensu,cread/sensu,keymone/sensu,bf4/sensu,quodlibetor/sensu,miyakawataku/sensu,javrasya/sensu