Refactor parsing variables to start runner agent

[npalm]

The way we parse runner parameters is becoming hard to maintain and extend. Some refactoring required.

Review on PR #1374

I think it might be better when working with these command to use a string array and then join then with a space. Rather than having to worry about spaces in all the strings etc.

runnerServiceConfig could be defined as a string array above and you can merge the arrays and join.

Originally posted by @ScottGuymer in #1374 (comment)

[ulich]

I would be happy to pick this up

[npalm]

Great, you help is very welcome!