Overwrite all environment params when an image build finishes

[leafty]

There may be outdated param values, etc. so we should overwrite all fields to be correct.

Ref: https://github.com/SwissDataScienceCenter/renku-data-services/pull/801/changes#diff-84d32bdd7436b97a5e74ee7582b19132cb68174c86492ab912fd9a256a098d04
=> change async def _refresh_build