fix PD peer svc update repeatly (#5015)

[ti-chi-bot]

This is an automated cherry-pick of #5015

What problem does this PR solve?

in #4973, we refactored the logic of PD service update, after that the PD peer service is updated repeatly.

I0519 09:53:29.198719       1 service_control.go:91] update Service: [default/tc-1-pd-peer] successfully, kind: TidbCluster, name: tc-1
I0519 09:54:29.199537       1 service_control.go:91] update Service: [default/tc-1-pd-peer] successfully, kind: TidbCluster, name: tc-1
I0519 09:55:29.220976       1 service_control.go:91] update Service: [default/tc-1-pd-peer] successfully, kind: TidbCluster, name: tc-1

This is because the service get from the cache may lack the pingcap.com/last-applied-configuration annotation as it is deleted by a previous reconcile. also see #462

tidb-operator/pkg/controller/service_control.go

Line 157 in e97423e

delete(oldSvc.Annotations, LastAppliedConfigAnnotation)

tidb-operator/pkg/controller/equality.go

Line 77 in e97423e

if lastAppliedConfig, ok := oldSvc.Annotations[LastAppliedConfigAnnotation]; ok {

What is changed and how does it work?

Code changes

• Has Go code change
• Has CI related scripts change

Tests

• Unit test
• E2E test
• Manual test
• No code

check not pd-peer service updated log after this fix.

Side effects

• Breaking backward compatibility
• Other side effects:

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation

Release Notes

Please refer to Release Notes Language Style Guide before writing the release note.

[ti-chi-bot]

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