XD-1442: Remove HadoopDistro enum

Remove enum and leverage the same trick as we did for the transport option.

Now, this will only work if the current working directory is ${xd.home}
Before going deeper here, I wanted to gather feedback on this.
Possible solutions are
- mess with the shell scripts to `cd` into xd.home
- make the AppContext/Environment available (ThreadLocal) to the handler, so that we can resolve ${xd.home}
- do nothing and assume users will be in the correct directory (?)