There is a difference in interpretation of what a block count is. neo-go nodes
currently respond to this request with the latest block number which is the
same number that neoscan.io shows. However, C# nodes deliberately do add one
to this number when answering to the getblockcount request to account for the
genesis block number 0.
This patch makes us consistent with C# nodes wrt to getblockcount behaviour.
de2eeb4671