core: Fix forcing close socket
core: Fix forcing close socket

This patch fixes the following warning when the cloud service
closes the connection. The current approach was forcing to close
the cloud (protocol) socket, even when HUP signal has been received.
(knotd:6016): GLib-WARNING **: Invalid file descriptor

CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source