Add test for ArgsManager::GetChainName
Add test for ArgsManager::GetChainName

There was some test coverage previously, but it was limited and didn't test
conflicting and negated arguments.


Former-commit-id: c43fd7ac47484e6d2e36221f60443ceadbb84285
syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin