unstable unit test ComputeServerRunner.multipleQuery

[JaySon-Huang]

Bug Report

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1. Minimal reproduce step (Required)

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

All unit test passed

3. What did you see instead (Required)

ComputeServerRunner.multipleQuery is not stable

https://ci.pingcap.net/blue/organizations/jenkins/tiflash-ghpr-unit-tests/detail/tiflash-ghpr-unit-tests/11643/pipeline

[2023-10-27T02:57:51.755Z] /home/jenkins/agent/workspace/tiflash-build-common/tiflash/dbms/src/Flash/tests/gtest_compute_server.cpp:742: Failure
[2023-10-27T02:57:51.755Z] Value of: assertQueryActive(gather_id.query_id)
[2023-10-27T02:57:51.755Z]   Actual: false (Query <query_ts:0, local_query_id:11, server_id:1, start_ts:11, resource_group: >not active
[2023-10-27T02:57:51.755Z] )
[2023-10-27T02:57:51.755Z] Expected: true

https://ci.pingcap.net/blue/organizations/jenkins/tiflash-ghpr-unit-tests/detail/tiflash-ghpr-unit-tests/11645/pipeline/
https://ci.pingcap.net/blue/rest/organizations/jenkins/pipelines/tiflash-ghpr-unit-tests/runs/11645/nodes/75/steps/80/log/?start=0

[2023-10-27T05:26:11.026Z] /home/jenkins/agent/workspace/tiflash-build-common/tiflash/dbms/src/Flash/tests/gtest_compute_server.cpp:742: Failure
[2023-10-27T05:26:11.026Z] Value of: assertQueryActive(gather_id.query_id)
[2023-10-27T05:26:11.026Z]   Actual: false (Query <query_ts:0, local_query_id:12, server_id:1, start_ts:12, resource_group: >not active
[2023-10-27T05:26:11.026Z] )
[2023-10-27T05:26:11.026Z] Expected: true

4. What is your TiFlash version? (Required)

test running with this PR: #8248

[SeaRise]

It seems that the query ends before canceling.
But it is not as expected, because before cancel, mock scan will continue to output block...

[xzhangxian1008]

It seems that the query ends because of timeout. And I think the timeout is caused by heavy system load. Not a bug.