Fix db_test2 parallelism (#8145)

Summary:
With thread/process-specific dirs. (Errors seen in FB infra.)

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8145

Test Plan: see in FB infra tests

Reviewed By: riversand963

Differential Revision: D27542355

Pulled By: pdillinger

fbshipit-source-id: b3c8e66f91a6a6b3a775f6fc0c3cf71e63c29ade

db/db_test2.cc

@@ -4116,7 +4116,7 @@ TEST_F(DBTest2, TraceWithFilter) {
 
   // Open another db, replay, and verify the data
   std::string value;
-  std::string dbname2 = test::TmpDir(env_) + "/db_replay";
+  std::string dbname2 = test::PerThreadDBPath(env_, "db_replay");
   ASSERT_OK(DestroyDB(dbname2, options));
 
   // Using a different name than db2, to pacify infer's use-after-lifetime
@@ -4167,7 +4167,7 @@ TEST_F(DBTest2, TraceWithFilter) {
   ASSERT_OK(DestroyDB(dbname2, options));
 
   // Set up a new db.
-  std::string dbname3 = test::TmpDir(env_) + "/db_not_trace_read";
+  std::string dbname3 = test::PerThreadDBPath(env_, "db_not_trace_read");
   ASSERT_OK(DestroyDB(dbname3, options));
 
   DB* db3_init = nullptr;
@@ -4584,7 +4584,7 @@ TEST_F(DBTest2, MultiDBParallelOpenTest) {
   Options options = CurrentOptions();
   std::vector<std::string> dbnames;
   for (int i = 0; i < kNumDbs; ++i) {
-    dbnames.emplace_back(test::TmpDir(env_) + "/db" + ToString(i));
+    dbnames.emplace_back(test::PerThreadDBPath(env_, "db" + ToString(i)));
     ASSERT_OK(DestroyDB(dbnames.back(), options));
   }