Simply route length generation code.

The old code had logic to use a shorter path length if we didn't
have enough nodes. But we don't support 2-node networks anwyay.

Fix for #9926.  I'm not calling this a bugfix on any particular
version, since a 2-node network would fail to work for you for a lot
of other reasons too, and it's not clear to me when that began, or if
2-node networks would ever have worked.