fix(core): remove extraneous RocksDB::CancelAllBackgroundWork calls (#3017)

[Ryan4253]

Closes #3017

Description of changes:

Removes extraneous calls to rocksdb::CancelAllBackgroundWork. See the issue for further explanation.

Test Plan:

Unit Test

[----------] Global test environment tear-down
[==========] 430 tests from 69 test suites ran. (20101 ms total)
[  PASSED  ] 429 tests.
[  SKIPPED ] 1 test, listed below:
[  SKIPPED ] UseBitmap/RedisBitmapTest.BitfieldStringGetSetTest/0

Logs

Before

2025/06/05-14:48:25.726530 66707 [db/db_impl/db_impl.cc:463] Shutdown: canceling all background work
2025/06/05-14:48:25.819216 66707 [db/db_impl/db_impl.cc:463] Shutdown: canceling all background work
2025/06/05-14:48:25.819338 66707 [db/db_impl/db_impl.cc:463] Shutdown: canceling all background work

After

2025/06/05-14:14:15.002071 42139 [db/db_impl/db_impl.cc:463] Shutdown: canceling all background work

[git-hulk]

@Ryan4253 It's expected to call this explicitly to prevent the data race between background threads and the db destructor, see https://github.com/apache/kvrocks/actions/runs/15493199236/job/43625063455?pr=3019#step:17:533.

[Ryan4253]

@git-hulk thanks for pointing it out! This should be a more correct version that would only cleanup once.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud