fix: retry on unknown error

[WenyXu]

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Refer to a related PR or issue link (optional)

What's changed and what's your intention?

It should retry on unknown error (e.g. incurring transport error)

2024-06-10T05:01:57.684978Z ERROR LocalManager::submit_root_procedure: common_procedure::local::runner: Failed to execute procedure metasrv-procedure::DropTable-4d04bd3d-3a0f-495c-819d-80b939475fa4, retry: false err=0: Failed to execute procedure due to external error
2024-06-10 13:01:57.685	
1: Failed to operate on datanode: peer-2(greptimedb-datanode-2.greptimedb-datanode.greptimedb:4001), at greptimedb/src/common/meta/src/ddl/utils.rs:33:27
2024-06-10 13:01:57.685	
2: External error, at greptimedb/src/client/src/region.rs:59:31
2024-06-10 13:01:57.685	
3: Failed to request RegionServer greptimedb-datanode-2.greptimedb-datanode.greptimedb:4001, code: Unknown error, at greptimedb/src/client/src/region.rs:193:31
2024-06-10 13:01:57.685	
4: transport error, at greptimedb/src/client/src/error.rs:176:23

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR requires documentation updates.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.17%. Comparing base (14a2d83) to head (d7af44a).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4138      +/-   ##
==========================================
- Coverage   85.47%   85.17%   -0.31%     
==========================================
  Files         994      994              
  Lines      174942   174942              
==========================================
- Hits       149535   149001     -534     
- Misses      25407    25941     +534     

[fengjiachun]

LGTM