[PLAT-111199] Terminate Statefulset only if enough pods are available

[yuchen-db]

this is to support minReadySeconds that solves the race condition during rolling update https://github.com/thanos-io/thanos/issues/4831#issuecomment-1503754747

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
2 out of 3 committers have signed the CLA.

:white_check_mark: christopherzli
:white_check_mark: yuchen-db
:x: jnyi
_{You have signed the CLA already but the status is still pending? Let us recheck it.}