Fix Katib e2e tests

[andreyvelich]

I made few changes in e2e test. I hope it will fix running problems.

1. Deleted part of creating ${GO_DIR}. According to this PR: fix: Remove copy #802, we deleted from some e2e test this part. I think it should fix problem with cp: cannot create symbolic link error.
2. Deleted NAMESPACE and REGISTRY env variable, since it is not needed.
3. Deleted part of describing pods and deploy in default namespace and other describe in some e2e test.
4. I left only describe appropriate Experiment in each e2e test. I think it is more informative.

/assign @johnugeorge @gaocegege

[andreyvelich]

/retest

[johnugeorge]

/lgtm
/approve

[kubeflow-bot]

This change is 

[andreyvelich]

/approve

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