Fix error variants in trustchain-ion utils

[thobson88]

These error variants are incorrect:

    // If call to get_network_info fails, return error
    client
        .get_network_info()
        .map_err(|_| VerifierError::LedgerClientError("getblockhash".to_string()))?;

    // Convert the block height to a block hash.
    let block_hash = client
        .get_block_hash(u64::from(block_height))
        .map_err(|_| VerifierError::InvalidBlockHeight(block_height.into()))?;