What problem does this PR solve?
fixes #1180
What is changed and how does it work?
e2e webhook is used to verify pods in upgrading however because we run e2e tests parallelly, the e2e webhook will reject pods in scaling in test now, so we should update it to take effect for tidb clusters in ugprading only
Check List
Tests
- Unit test
- E2E test
Does this PR introduce a user-facing change?:
release-note
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