Cleanup cf handlers before deleting db (#8564)

Summary:
Delete column family handlers before deleting db to avoid `last_ref`
assert.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8564

Test Plan: Inject compaction test in db_stress test

Reviewed By: pdillinger

Differential Revision: D29797375

Pulled By: jay-zhuang

fbshipit-source-id: e8baf4d279f4db5d963db95c9445454156205501

db_stress_tool/db_stress_test_base.cc

@@ -2563,7 +2563,12 @@ void StressTest::Open() {
             s = static_cast_with_check<DBImpl>(db_->GetRootDB())
                     ->TEST_WaitForCompact(true);
             if (!s.ok()) {
+              for (auto cf : column_families_) {
+                delete cf;
+              }
+              column_families_.clear();
               delete db_;
+              db_ = nullptr;
             }
           }
           if (!s.ok()) {