unstable test TestDDLScheduling

[hawkingrei]

Bug Report

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1. Minimal reproduce step (Required)

  job_table_test.go:166: 
        	Error Trace:	/home/jenkins/.tidb/tmp/63a9840cd0739f2c243bb46478607469/sandbox/processwrapper-sandbox/5842/execroot/__main__/bazel-out/k8-fastbuild/bin/ddl/ddl_test_/ddl_test.runfiles/__main__/ddl/job_table_test.go:166
        	            				/home/jenkins/.tidb/tmp/63a9840cd0739f2c243bb46478607469/sandbox/processwrapper-sandbox/5842/execroot/__main__/bazel-out/k8-fastbuild/bin/ddl/ddl_test_/ddl_test.runfiles/__main__/ddl/job_table_test.go:175
        	            				/home/jenkins/.tidb/tmp/63a9840cd0739f2c243bb46478607469/sandbox/processwrapper-sandbox/5842/execroot/__main__/bazel-out/k8-fastbuild/bin/ddl/ddl_test_/ddl_test.runfiles/__main__/ddl/job_table_test.go:131
        	Error:      	Should be false
        	Test:       	TestDDLScheduling

https://do.pingcap.net/jenkins/blue/rest/organizations/jenkins/pipelines/pingcap/pipelines/tidb/pipelines/ghpr_unit_test/runs/1505/nodes/49/steps/52/log/?start=0

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

3. What did you see instead (Required)

4. What is your TiDB version? (Required)