Skip fsync in txn tests (#7641)

Summary:
The tests often times out in internal infra, skipping fsync should reduce test time.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7641

Test Plan: watch existing tests to pass

Reviewed By: anand1976

Differential Revision: D24765098

Pulled By: cheng-chang

fbshipit-source-id: c62bf8110361aee901918d632cf4772435d05e8d

utilities/transactions/transaction_test.h

@@ -62,6 +62,7 @@ class TransactionTestBase : public ::testing::Test {
     options.unordered_write = write_ordering == kUnorderedWrite;
     options.level0_file_num_compaction_trigger = 2;
     options.merge_operator = MergeOperators::CreateFromStringId("stringappend");
+    special_env.skip_fsync_ = true;
     env = new FaultInjectionTestEnv(&special_env);
     options.env = env;
     options.two_write_queues = two_write_queue;