Consider doing the db upgrade in an init container

[artntek]

Problem: initial DB upgrade makes metacat unresponsive, so k8s restarts the pod

We should consider doing the db upgrade in an init container, so that metacat won't be started until the upgrade is done

For the knb corpus, the initial DB upgrade from 2.19.0 -> 3.0.0 took about 3-1/2 hours on the dev cluster (metacat running on k8s-dev-node-3 (slower machine); postgres on k8s-dev-node-5 (faster machine)).

During this time, liveness and readiness probes timed out because metacat was completely unresponsive, so k8s restarted the pod.

The workaround was temporarily to set:

livenessProbe:
  enabled: false
readinessProbe:
  enabled: false

and then switch back after the upgrade was complete.

Note that log4j was set to DEBUG level for the first 3 hours. Not sure if this slowed things down significantly?