zoekt-indexserver: sometimes does not delete old indexes on rename

Created by: keegancsmith

This leads to some graphQL requests failing. However, due to us filtering results we get back from zoekt this doesn't seem to affect normal search queries. However, directly inspecting cse-k8s zoekt-indexserver shows an old index (and the new index) on disk. My suspicion is the root cause is from us switching cleanup from being name based to ID based.

See original report https://github.com/sourcegraph/sourcegraph/issues/29597. Hopefully resolving this resolves the original report.