[deploy-sourcegraph] pgsql pod can't start when migrating 3.0.0-beta.3 -> 3.0.1-rc3

Created by: ggilmore

Steps to reproduce:

1. Deploy https://github.com/sourcegraph/deploy-sourcegraph/commit/35c7d102fc768e00aa9ae9ad0590ab9acf081d05 to a K8s cluster
2. Add a repository, do a search, see that it passes a smoke test
3. Deploy https://github.com/sourcegraph/deploy-sourcegraph/commit/7edcadbc3ebf46cb1bc1198f8a3e359a2380e22a to a cluster

Expected behavior:

All the pods in the cluster are healthy

Actual behavior:

The psgql pod never becomes healthy. The pgsql container is in CrashLoopBackOff and shows the following logs:

pg_ctl: another server might be running; trying to start server anyway
waiting for server to start.... stopped waiting
pg_ctl: could not start server
Examine the log output.