Check if the task is still running according to the scheduler before changing the status

Checks if the task is still running according to the scheduler before changing the status. @Souf149 Could you perhaps verify the fix?

Please check if the tasks are kept to FAILED for a failing nmap-tcp!

[x] All the commits in this PR are properly PGP-signed and verified.
[x] This PR only contains functionality relevant to the issue.
[x] I have written unit tests for the changes or fixes I made.
[x] I have checked the documentation and made changes where necessary.
[x] I have performed a self-review of my code and refactored it to the best of my abilities.

Checklist for code reviewers:

Copy-paste the checklist from the docs/source/templates folder into your comment.

Copy-paste the checklist from the docs/source/templates folder into your comment.