3900a8f: Continue on failure to pull / push from kaas caches (#11)

* Removing the tag latest and moving to a tag system based on the version
of the file containing the test set being run i.e. run_kontrol.sh

If a download from the cache server fails this should not fail the test
overall. It will just take longer.

	modified:   .github/workflows/optimism-ci.yaml

* If uploading the latest cache fails it does not mean the test itself
failed. Do not stop or fail a test because this upload step failed.