Improve e2e troubleshooting (#448)

* Improve e2e troubleshooting

Improve / fix some issues with e2e tests:
- Add more logs; print some useful information such as when cluster is
  still up
- Improve readiness (e.g: had agents pods crashing)
- Use more up to date templates for loki and kafka (similar to what we
  have in docs repo)

* remove -a flag; do not tag e2e

Tagging e2e is not necessary and has some undesired side effect such as
excluding these e2e source files from building/linting, which can
invisibilise some problems

* Add doc