subtask is taken as scheduled away mistakenly, cause it rerun

[D3Hunter]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

• checkBalanceSubtask routine runs GetSubtasksByExecIDAndStepAndStates
• outer runSubtask finishes and cancel check-context
• and trigger this query returns incorrect result when context done in the middle #50089, so GetSubtasksByExecIDAndStepAndStates returns no error and no result.
• subtask taken as schedule away and cancel run-step-context, and rerun

[2024/01/29 19:01:49.509 +00:00] [Info] [task_executor.go:121] ["subtask is scheduled away, cancel running"] [task-id=1] [task-type=ImportInto]

but the subtask is not balanced in this time period

[2024/01/29 19:10:35.198 +00:00] [INFO] [balancer.go:203] [\"balance subtasks\"] [subtasks=\"[\\\"Subtask[ID=684, Step=5, Type=ImportInto, TaskID=1, State=pending, ExecID=tc-tidb-7.tc-tidb-peer.testbed-global-40t-gcp-tps-6390392-1-944.svc:4000]\\\"]\"]"
[2024/01/29 19:02:57.531 +00:00] [INFO] [balancer.go:203] [\"balance subtasks\"] [subtasks=\"[\\\"Subtask[ID=684, Step=5, Type=ImportInto, TaskID=1, State=pending, ExecID=tc-tidb-10.tc-tidb-peer.testbed-global-40t-gcp-tps-6390392-1-944.svc:4000]\\\"]\"]"
[2024/01/29 18:53:28.281 +00:00] [INFO] [balancer.go:203] [\"balance subtasks\"] [subtasks=\"[\\\"Subtask[ID=684, Step=5, Type=ImportInto, TaskID=1, State=pending, ExecID=tc-tidb-0.tc-tidb-peer.testbed-global-40t-gcp-tps-6390392-1-944.svc:4000]\\\"]\"]"

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

subtask run once

3. What did you see instead (Required)

run twice

4. What is your TiDB version? (Required)

master