fix handling incoming connections by node

So I may have missed something, but it seems to be that in current version bin/bitcoin_node is incapable of accepting incoming connections.

One thing is this max connections_in check which seems to be on the wrong side.

And the other is I don't see where it ever sends version for an incoming connection. So I changed it to send after connection is initialized, just as it is for outgoing. If there was any reason to separate those cases then please explain why so I can fix it in another way (and put some comment with explanation).