[OS-3559] Rewrite completely Rally tester
The reasons why:
- We don't need a lot of the complexity in there
- We don't send results via Flume and we needed another way to send the results and see them in a dashboard (reading directly with Morphlines)
- Lot of the fields that we were sending are not necessary and add complexity to the code
- Some refactoring in addition to it
- Possibility of adding multiple emails