Revert env for katib-db

[hougangliu]

What this PR does / why we need it:

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

1. Please confirm that if this PR changes any image versions, then that's the sole change this PR makes.

Release note:

---

This change is 

[hougangliu]

@gaocegege @johnugeorge this PR is just a temporary fix so that we can build 0.7.0 image. we need investigate further to fix it.
@johnugeorge after this PR builds image, please replace gcr.io/kubeflow-ci/katib/v1alpha3/katib-manager:latest in kubeflow/manifests#563 to check if it works
If it works, please merge this PR and tag katib 0.7.0 images then.

[gaocegege]

Do you know why it works?

[gaocegege]

/lgtm
/approve

It is a temp fix for CI in manifests.

[k8s-ci-robot]

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