Flaky integration test `txn_cleanup_2pc_locks`

[pingyu]

See https://github.com/tikv/client-rust/actions/runs/6940223881/job/18878804812 commit d440f068f48355da04d3642094939b0fb0111801

     Running tests/failpoint_tests.rs (target/debug/deps/failpoint_tests-6486f001f7ac1501)

running 5 tests
init finish with 292 regions
test txn_cleanup_2pc_locks has been running for over 60 seconds
test txn_cleanup_async_commit_locks has been running for over 60 seconds
test txn_cleanup_locks_batch_size has been running for over 60 seconds
test txn_cleanup_range_async_commit_locks has been running for over 60 seconds
thread 'txn_cleanup_2pc_locks' panicked at src/pd/cluster.rs:270:47:
called `Option::unwrap()` on a `None` value
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
thread 'txn_cleanup_2pc_locks' panicked at src/pd/cluster.rs:270:47:
called `Option::unwrap()` on a `None` value
thread 'txn_cleanup_2pc_locks' panicked at src/pd/cluster.rs:270:47:
called `Option::unwrap()` on a `None` value
thread 'txn_cleanup_2pc_locks' panicked at src/pd/cluster.rs:270:47:
called `Option::unwrap()` on a `None` value
thread 'txn_cleanup_2pc_locks' panicked at src/pd/cluster.rs:270:47:
called `Option::unwrap()` on a `None` value
thread 'txn_cleanup_2pc_locks' panicked at src/pd/cluster.rs:270:47:
called `Option::unwrap()` on a `None` value
thread 'txn_cleanup_2pc_locks' panicked at src/pd/cluster.rs:270:47:
called `Option::unwrap()` on a `None` value
thread 'txn_cleanup_2pc_locks' panicked at src/pd/cluster.rs:270:47:
called `Option::unwrap()` on a `None` value
thread 'txn_cleanup_2pc_locks' panicked at src/pd/cluster.rs:270:47:
called `Option::unwrap()` on a `None` value
thread 'txn_cleanup_2pc_locks' panicked at src/pd/cluster.rs:270:47:
called `Option::unwrap()` on a `None` value
make: *** [Makefile:26: integration-test] Terminated