Removing minitest from the katello rpm spec

Given that we run unit tests under travis after every commit,
running em again while building rpm feel redundant.
Also we were using minitest only as "source code linting" tool.
Rubocop will catch many more of those in travis.
So no point for having minitest in rpm spec and having to maintain it.
Removing them from the spec

Also contains rubo cop changes.
999075-dist-events - fix bug and update method for updating distributor tasks

999075-dist-events - removed TaskStatus.refresh() call from distributor.rb since only applies to pulp

999075-dist-events - ...and removing the now-useless wrapper method in distributor.rb
Merge pull request #2834 from parthaa/minus-minitest

Removing minitest from the katello rpm spec
Merge pull request #2833 from thomasmckay/999075-dist-events

999075-dist-events - fix bug and update method for updating distributor ...