Mainnet nodes occasionally report Classic block heights

[shemnon]

Occasionally the prometheus metrics report the Ethereum Classic chain height as the Mainnet chain height.

What I think is going on is that there is a short period of time between when we handshake a peer and consider it a full peer when we ask some things of the node, such as what their dao block hash is. During that period the peer is still in the collections that are used to (a) query height and (b) query total node count. To fix this we need to interrogate the node prior to "full peer admission" whatever that looks like.