server: make shutdown nearing to an end
server: make shutdown nearing to an end

Be a bit more verbose on what's going on, and just shut down if there
seems to be no more progress with sending data.

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