[core] Add improved logging for unexpected peer_ids

If a peer sends a HandshakeMessage with a 'peer_id' that *does not*
match the 'peer_id' it sent to the tracker - log both the expected
and actual peer_ids.

Helps diagnose #614

It's probably a normal bittorrent client which is just randomising
the peer id on every connection attempt.

src/MonoTorrent.Client/MonoTorrent.Client.Modes/Mode.cs

@@ -226,7 +226,7 @@ protected virtual void HandleHandshakeMessage (PeerId id, HandshakeMessage messa
                     // match we should close the connection. I *think* uTorrent doesn't randomise peerids
                     // for private torrents. It's not documented very well. We may need to relax this check
                     // if other clients randomize for private torrents.
-                    logger.Info (id.Connection, "HandShake.Handle - Invalid peerid");
+                    logger.InfoFormatted (id.Connection, "HandShake.Handle - Invalid peerid. Expected '{0}' but received '{1}'", id.Peer.Info.PeerId, message.PeerId);
                     throw new TorrentException ("Supplied PeerID didn't match the one the tracker gave us");
                 } else {
                     // We don't care about the mismatch for public torrents. uTorrent randomizes its PeerId, as do other clients.

src/MonoTorrent.Client/MonoTorrent.Logging/Logger.cs

@@ -106,6 +106,12 @@ internal void InfoFormatted (IPeerConnection connection, string formatString, ob
                 Writer.Info ($"{connection.Uri}: {string.Format (formatString, p1)}");
         }
 
+        internal void InfoFormatted (IPeerConnection connection, string formatString, object p1, object p2)
+        {
+            if (Writer != null)
+                Writer.Info ($"{connection.Uri}: {string.Format (formatString, p1, p2)}");
+        }
+
         internal void Error (string message)
         {
             if (Writer != null)