Nodes should always advertise after seeing a new epoch #216
Description
Currently, nodes don't send route advertisements if nothing has changed in the connection table they would be sending, to avoid unnecessary traffic. However, this means that under certain circumstances, when a new (non-ephemeral) node comes on-line that is reusing the same node-id as a previously seen node, the new node can fail to receive information about other non-directly-connected nodes on the mesh.
To fix this, when a node receives a routing advertisement broadcast from an already-known node and the epoch is different, it should note this fact and not suppress its own subsequent advertisement.
(Making an issue for this so I don't forget about it.)