Fix way of checking node's build type

Because @lswiszcz fixed issue hive#155 (closed), node started to return non-zero exit codes in case of error during command line arguments parsing.

This was motivation to rewrite mechanism of checking node's executable build version (testnet or mainnet).

Previously it was checked with workaround/trick/hack. For test, given executable was run with flag which is known only in testnet. So mainnet reported error about unknown flag. In case of testnet different error was reported. This difference was used to distinguish between testnet and mainnet.

Now it was rewritten in a civilized way by @kmochocki. Currently Hived can return node build type with --version flag, so TestTools just read it :)

Changes are related to: hive!715 (merged)

Author: @kmochocki
Reviewers: @mzebrak @pbatko
FYI: @lswiszcz