[BUG] sysbench-test is instability, sometimes coredump

[nauta]

Describe the bug
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ref: https://github.com/nautaa/miniob/actions/runs/9042402084
It seems to be related to index file persistence.
** Environment**
Environment Details sometimes important

• OS Version:
• CPU Arch(x86/arm):
• Compiler:
• Others:

Fast Reproduce Steps(Required)
Steps to reproduce the behavior:

1. set sysbench table_size = 100; // relatively small
2. run sysbench miniob_select prepare
3. run sysbench miniob_select run
4. killall observer
5. restart observer
   ref: https://github.com/oceanbase/miniob/compare/main...nautaa:miniob:test_sysbench_2?expand=1

Expected behavior
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Actual Behavior
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Additional context
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