Make CLIMainTest easier to run against remote CDAP instances

I'm unaware of the complete context of this PR, so my feedback is based only upon looking at these two files :)

The only two things that I can see have changed (other than refactoring which LGTM) are 
- ``PREFIX`` is added to ``streamId`` and ``datasetId``. However, I don't see where it is used in this PR. Just standardization?
- timeouts are added in ``CLIConfig`` below. Was there a reason for this?