data race found in the domain owner

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Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

dm unit test failed, and report data race from the domain owner manager

2. What did you expect to see? (Required)

run normally

3. What did you see instead (Required)

WARNING: DATA RACE
Read at 0x00c009bf65d8 by goroutine 2545:
  github.com/pingcap/tidb/pkg/owner.(*mockManager).toBeOwner()
      /go/pkg/mod/github.com/pingcap/[email protected]/pkg/owner/mock.go:91 +0x364
  github.com/pingcap/tidb/pkg/owner.(*mockManager).CampaignOwner.func1()
      /go/pkg/mod/github.com/pingcap/[email protected]/pkg/owner/mock.go:157 +0x43d

Previous write at 0x00c009bf65d8 by goroutine 448:
  github.com/pingcap/tidb/pkg/owner.(*mockManager).SetListener()
      /go/pkg/mod/github.com/pingcap/[email protected]/pkg/owner/mock.go:181 +0x39
  github.com/pingcap/tidb/pkg/domain.(*Domain).UpdateTableStatsLoop()
      /go/pkg/mod/github.com/pingcap/[email protected]/pkg/domain/domain.go:2389 +0x7b4
  github.com/pingcap/tidb/pkg/domain.(*Domain).LoadAndUpdateStatsLoop()
      /go/pkg/mod/github.com/pingcap/[email protected]/pkg/domain/domain.go:2353 +0x75
  github.com/pingcap/tidb/pkg/session.bootstrapSessionImpl()
      /go/pkg/mod/github.com/pingcap/[email protected]/pkg/session/session.go:3629 +0x1b57
  github.com/pingcap/tidb/pkg/domain.(*Domain).rebuildSysVarCache()
      /go/pkg/mod/github.com/pingcap/[email protected]/pkg/domain/sysvar_cache.go:143 +0xa34
  github.com/pingcap/tidb/pkg/sessionctx/variable.init.func215()
      /go/pkg/mod/github.com/pingcap/[email protected]/pkg/sessionctx/variable/sysvar.go:1129 +0x52
  github.com/pingcap/tidb/pkg/sessionctx/variable.(*SysVar).ValidateWithRelaxedValidation()
      /go/pkg/mod/github.com/pingcap/[email protected]/pkg/sessionctx/variable/variable.go:377 +0x242
  github.com/pingcap/tidb/pkg/domain.(*Domain).rebuildSysVarCache()
      /go/pkg/mod/github.com/pingcap/[email protected]/pkg/domain/sysvar_cache.go:142 +0x9c4
  github.com/pingcap/tidb/pkg/sessionctx/variable.parseSchemaCacheSize()
      /go/pkg/mod/github.com/pingcap/[email protected]/pkg/sessionctx/variable/varsutil.go:638 +0x17c
  github.com/pingcap/tidb/pkg/sessionctx/variable.init.func618()
      /go/pkg/mod/github.com/pingcap/[email protected]/pkg/sessionctx/variable/sysvar.go:3296 +0x67
  github.com/pingcap/tidb/pkg/domain.(*Domain).rebuildSysVarCache()
      /go/pkg/mod/github.com/pingcap/[email protected]/pkg/domain/sysvar_cache.go:143 +0xa34
  github.com/pingcap/tidb/pkg/sessionctx/variable.init.func617()
      /go/pkg/mod/github.com/pingcap/[email protected]/pkg/sessionctx/variable/sysvar.go:3288 +0x52
  github.com/pingcap/tidb/pkg/sessionctx/variable.(*SysVar).ValidateWithRelaxedValidation()
      /go/pkg/mod/github.com/pingcap/[email protected]/pkg/sessionctx/variable/variable.go:377 +0x242
  github.com/pingcap/tidb/pkg/domain.(*Domain).rebuildSysVarCache()
      /go/pkg/mod/github.com/pingcap/[email protected]/pkg/domain/sysvar_cache.go:142 +0x9c4
  fmt.Sscanf()
      /usr/local/go/src/fmt/scan.go:114 +0x18e
  github.com/pingcap/tidb/pkg/sessionctx/variable.parseByteSize()

4. What is your TiDB version? (Required)

master