[BUG] only set safe_to_destroy when all data on memtable has been synced

unittest/storage/test_compaction_policy.cpp

@@ -369,7 +369,6 @@ int TestCompactionPolicy::mock_memtable(
     memtable->write_ref_cnt_ = 0;
     memtable->unsubmitted_cnt_ = 0;
     memtable->is_tablet_freeze_ = true;
-    memtable->state_ = ObMemtableState::MINOR_FROZEN;
     memtable->set_resolved_active_memtable_left_boundary(true);
     memtable->set_frozen();
     memtable->location_ = storage::checkpoint::ObFreezeCheckpointLocation::PREPARE;