Make DBTestUniversalCompaction.IncreaseUniversalCompactionNumLevels more deterministic

Summary: DBTestUniversalCompaction, IncreaseUniversalCompactionNumLevels fails one in about 30 runs when running in parallel. We wait for compaction after each flush to make the compaction behavior deterministic.

Test Plan: Run the test 1000 times in parallel and it still passes.

Reviewers: yhchiang, IslamAbdelRahman

Reviewed By: IslamAbdelRahman

Subscribers: kradhakrishnan, yiwu, leveldb, andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D56841

db/db_universal_compaction_test.cc

@@ -1091,6 +1091,7 @@ TEST_P(DBTestUniversalCompaction, IncreaseUniversalCompactionNumLevels) {
     // each value is 10K
     ASSERT_OK(Put(1, Key(i), RandomString(&rnd, 10000)));
     dbfull()->TEST_WaitForFlushMemTable(handles_[1]);
+    dbfull()->TEST_WaitForCompact();
   }
   ASSERT_OK(Flush(1));
   dbfull()->TEST_WaitForCompact();
@@ -1108,6 +1109,7 @@ TEST_P(DBTestUniversalCompaction, IncreaseUniversalCompactionNumLevels) {
     // each value is 10K
     ASSERT_OK(Put(1, Key(i), RandomString(&rnd, 10000)));
     dbfull()->TEST_WaitForFlushMemTable(handles_[1]);
+    dbfull()->TEST_WaitForCompact();
   }
   ASSERT_OK(Flush(1));
   dbfull()->TEST_WaitForCompact();
@@ -1139,6 +1141,7 @@ TEST_P(DBTestUniversalCompaction, IncreaseUniversalCompactionNumLevels) {
     // each value is 10K
     ASSERT_OK(Put(1, Key(i), RandomString(&rnd, 10000)));
     dbfull()->TEST_WaitForFlushMemTable(handles_[1]);
+    dbfull()->TEST_WaitForCompact();
   }
   ASSERT_OK(Flush(1));
   dbfull()->TEST_WaitForCompact();