For route discovery connections, 2 logical channels are used:
One channel for netflood messages, and one for unicast.
When opening a route discovery connection using
route_discovery_open(), only the netflood channel number is
specified, and the unicast channel number is hard-coded to be the
next channel (+1).
This commit adds an alternative function for opening
route-discovery connections, allowing the user to specify both
channels independently, to gain improved control and readability.
1b8c889e41