Allow clean K6 object when test has failed or finished OK

[aaguilartablada]

To solve the issue https://github.com/grafana/k6-operator/issues/275

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
1 out of 2 committers have signed the CLA.

:white_check_mark: aaguilartablada
:x: Álvaro Aguilar

---

Álvaro Aguilar seems not to be a GitHub user. You need a GitHub account to be able to sign the CLA. If you have already a GitHub account, please add the email address used for this commit to your account.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}