tests: fix leak test in embeded etcd test (#1916)

[ti-chi-bot]

This is an automated cherry-pick of #1916

What problem does this PR solve?

Fix a leak in test from CI

[2021-06-02T11:43:34.661Z] ----------------------------------------------------------------------
[2021-06-02T11:43:34.661Z] FAIL: etcd_test.go:53: etcdSuite.TestEmbedEtcd
[2021-06-02T11:43:34.661Z] 
[2021-06-02T11:43:34.661Z] etcd_test.go:74:
[2021-06-02T11:43:34.661Z]     ...
[2021-06-02T11:43:34.661Z] /home/jenkins/agent/workspace/cdc_ghpr_leak_test/go/src/github.com/pingcap/ticdc/pkg/util/testleak/leaktest.go:162:
[2021-06-02T11:43:34.661Z]     c.Errorf("Test %s check-count %d appears to have leaked: %v", c.TestName(), cnt, g)
[2021-06-02T11:43:34.661Z] ... Error: Test etcdSuite.TestEmbedEtcd check-count 50 appears to have leaked: github.com/pingcap/ticdc/pkg/etcd.(*etcdSuite).SetUpTest.func1(0xc00022a4b0, 0xc00003f080)
[2021-06-02T11:43:34.661Z] 	/home/jenkins/agent/workspace/cdc_ghpr_leak_test/go/src/github.com/pingcap/ticdc/pkg/etcd/etcd_test.go:45 +0x6d
[2021-06-02T11:43:34.661Z] created by github.com/pingcap/ticdc/pkg/etcd.(*etcdSuite).SetUpTest
[2021-06-02T11:43:34.661Z] 	/home/jenkins/agent/workspace/cdc_ghpr_leak_test/go/src/github.com/pingcap/ticdc/pkg/etcd/etcd_test.go:44 +0x172
[2021-06-02T11:43:34.661Z] 
[2021-06-02T11:43:34.661Z] OOPS: 4 passed, 1 FAILED
[2021-06-02T11:43:34.661Z] --- FAIL: Test (28.03s)
[2021-06-02T11:43:34.661Z] FAIL
[2021-06-02T11:43:34.661Z] FAIL	github.com/pingcap/ticdc/pkg/etcd	28.104s

What is changed and how it works?

Remove the log error goroutine, log error when test shutdown

Check List

Tests

• Unit test
• Integration test

Release note

• No release note

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• amyangfei
• lonng

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[lonng]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: b4e5854

[codecov-commenter]

Codecov Report

Merging #1944 (b4e5854) into release-5.0 (a1067a0) will increase coverage by 0.0242%.
The diff coverage is n/a.

@@                 Coverage Diff                 @@
##           release-5.0      #1944        +/-   ##
===================================================
+ Coverage      53.8503%   53.8746%   +0.0242%     
===================================================
  Files              155        155                
  Lines            16479      16479                
===================================================
+ Hits              8874       8878         +4     
- Misses            6655       6656         +1     
+ Partials           950        945         -5