lib/connections:  Indicate stack in transport (fixes #4463)
lib/connections:  Indicate stack in transport (fixes #4463)

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4486

AudriusButkevicius/syncthing,rumpelsepp/syncthing,syncthing/syncthing,wweich/syncthing,jryans/syncthing,xduugu/syncthing,lkwg82/syncthing,jryans/syncthing,jryans/syncthing,jryans/syncthing,xduugu/syncthing,syncthing/syncthing,imsodin/syncthing,imsodin/syncthing,AudriusButkevicius/syncthing,rumpelsepp/syncthing,wweich/syncthing,imsodin/syncthing,uok/syncthing,rumpelsepp/syncthing,imsodin/syncthing,lkwg82/syncthing,lkwg82/syncthing,rumpelsepp/syncthing,syncthing/syncthing,AudriusButkevicius/syncthing,xduugu/syncthing,AudriusButkevicius/syncthing,syncthing/syncthing,imsodin/syncthing,lkwg82/syncthing,syncthing/syncthing,uok/syncthing,syncthing/syncthing,uok/syncthing,uok/syncthing,wweich/syncthing,wweich/syncthing,xduugu/syncthing