Fix UBSAN Error in WritePreparedTransactionTest

Summary:
WritePreparedTransactionTest has the UBSAN error because the wrong order of its parent class construction. Fix it.
Closes https://github.com/facebook/rocksdb/pull/3478

Differential Revision: D6928975

Pulled By: siying

fbshipit-source-id: 13edfd5cb9cf73f1ac5ae3b6f53061d32783733d

utilities/transactions/write_prepared_transaction_test.cc

@@ -349,7 +349,7 @@ class WritePreparedTransactionTestBase : public TransactionTestBase {
 
 class WritePreparedTransactionTest
     : public WritePreparedTransactionTestBase,
-      public ::testing::WithParamInterface<
+      virtual public ::testing::WithParamInterface<
           std::tuple<bool, bool, TxnDBWritePolicy>> {
  public:
   WritePreparedTransactionTest()