dispatch_connection: drop pointless work in cleanup
dispatch_connection: drop pointless work in cleanup

We no longer are removing a connection slot, we simply flag it as being
available for reuse, so no need to lookup the connection in the
connection table, and possibly find inconsistencies, since they cannot
happen, we got a pointer from an array.

grobian/carbon-c-relay,grobian/carbon-c-relay,rtoma/carbon-c-relay,piotr1212/carbon-c-relay,rtoma/carbon-c-relay,zzl0/carbon-c-relay,tjamesturner/carbon-c-relay,piotr1212/carbon-c-relay,lyft/carbon-c-relay,lyft/carbon-c-relay,Skyscanner/carbon-c-relay,zzl0/carbon-c-relay,grobian/carbon-c-relay,lyft/carbon-c-relay,piotr1212/carbon-c-relay,piotr1212/carbon-c-relay,Skyscanner/carbon-c-relay,tjamesturner/carbon-c-relay