Prevent pod restarts caused by slow db boot

[lkpdn]

When we run ./scripts/deploy.sh for the first time, vizier-core is highly likely to undergo a few times of "Pod Restart". This is because vizier-db takes much longer time to become ready. This PR intends to have vizier-core wait for DB to become ready, so that we no longer see any pod Restart if all components are properly deployed.

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This change is 

[k8s-ci-robot]

Hi @lkpdn. Thanks for your PR.

I'm waiting for a kubeflow member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[YujiOshima]

/ok-to-test

[lkpdn]

#260 has been merged so let me rebase this (branch: prevent-pod-restarts-caused-by-slow-db-boot) to master, otherwise it would blind both vizier-db and vizier-core from that Secret.

[lkpdn]

Please take another look: dc7bb07
Thanks.

[lkpdn]

My apologies for the lack of test. I cooked + fixed up commit so please review this one:
88cfaca ccd034e .

[lkpdn]

@toshiiw thanks for reviewing, PTAL: 2ae5826

[YujiOshima]

@lkpdn Thanks, great!
/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: YujiOshima

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[lkpdn]

@YujiOshima thanks :)