Add more sync point to fix flaky test GroupCommitTest

Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/4637

Differential Revision: D12963727

Pulled By: miasantreble

fbshipit-source-id: 76053501afbecc6ef388ddc56542fa0185243e3f

db/db_test.cc

@@ -2351,7 +2351,9 @@ TEST_F(DBTest, GroupCommitTest) {
 
     rocksdb::SyncPoint::GetInstance()->LoadDependency(
         {{"WriteThread::JoinBatchGroup:BeganWaiting",
-          "DBImpl::WriteImpl:BeforeLeaderEnters"}});
+          "DBImpl::WriteImpl:BeforeLeaderEnters"},
+          {"WriteThread::AwaitState:BlockingWaiting",
+          "WriteThread::EnterAsBatchGroupLeader:End"}});
     rocksdb::SyncPoint::GetInstance()->EnableProcessing();
 
     // Start threads

db/write_thread.cc

@@ -181,6 +181,7 @@ uint8_t WriteThread::AwaitState(Writer* w, uint8_t goal_mask,
   }
 
   if ((state & goal_mask) == 0) {
+    TEST_SYNC_POINT_CALLBACK("WriteThread::AwaitState:BlockingWaiting", w);
     state = BlockingAwaitState(w, goal_mask);
   }