Bitnami update breaks post `v0.4.0` releases

[iameskild]

The [recent decision by bitnami to remove older helm charts from their default index.yaml has essentially broken qhub deploy for all of our post v0.4.0 releases. At this point, I believe it makes sense to cherry-pick the most recent PR (which resolves this issue going-forward) and cut a new release asap. I’d be happy to handle this on Wednesday (June 8th).

[trallard]

Backport to 0.4.1 and 0.4.0