connectors-ci: abusive re-use of cache

[alafanechere]

We can have the impression that is some context the test pipeline running on PR is abusively caching connector images:

• Even on code change the docker image is not always rebuilt
• CAT seems running on the wrong connector image

This happened specifically on #27658
I also suspect that this CAT failure can be related to an abusive cache / image re-use.

These problems can't be reproduced locally.

[alafanechere]

I think #27858 will reduce the moving parts and improve isolation to avoid this kind of problem.

[alafanechere]

This issue might be partly solved by the upgrade to Dagger 0.6.4.
But we still observe transient failures on nightly cat, hopefully it will be solved by #27858

[alafanechere]

CAT seems running on the wrong connector image

#28656 fixed it, it was not the wrong connector image but the wrong connector secret.