net.c: Let net_disconnect() perform an asynchronous disconnect
net.c: Let net_disconnect() perform an asynchronous disconnect

This makes sure a disconnect won't block even when more I/O is required
than a force close of the connection. (E.g. graceful disconnect, or a
clean TLS disconnect)

srijan/ncdc,srijan/ncdc,Tilka/ncdc,srijan/ncdc,Tilka/ncdc