[tests] Move only: move NodeConnCB below NodeConn
[tests] Move only: move NodeConnCB below NodeConn

This is required since NodeConnCB will inherit from NodeConn
after the next commit.

chaincoin/chaincoin,chaincoin/chaincoin,chaincoin/chaincoin,chaincoin/chaincoin,chaincoin/chaincoin,chaincoin/chaincoin