Fix TSAN version of TestRedisService.TestHMGetTiming

Summary:
Applying so many parallel commands timeouts in TSAN build.
Changed to sync by smaller portions.

Test Plan: ybd tsan --cxx-test redisserver_redisserver-test --gtest_filter TestRedisService.TestHMGetTiming -n 100

Reviewers: mikhail, amitanand, timur

Reviewed By: timur

Subscribers: ybase

Differential Revision: https://phabricator.dev.yugabyte.com/D4657

src/yb/yql/redis/redisserver/redisserver-test.cc

@@ -2598,6 +2598,9 @@ TEST_F(TestRedisService, TestHMGetTiming) {
       string sj = std::to_string(j);
       DoRedisTestInt(__LINE__, {"HSET", "parent_" + si, "subkey_" + sj, "value_" + sj}, 1);
     }
+    if (IsSanitizer() || ((i & 0x7) == 0)) {
+      SyncClient();
+    }
   }
 
   SyncClient();