Fix msvc debug test failures (#6579)

Summary:
1. stats_history_test: one slice of stats history is 12526 Bytes, which is greater than original assumption.
![image](https://user-images.githubusercontent.com/17753898/77381970-5a611a80-6d3c-11ea-9d64-59d2e3c04f79.png)
2. table_test: in VerifyBlockAccessTrace function, release trace reader before delete trace file.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6579

Reviewed By: siying

Differential Revision: D20767373

Pulled By: pdillinger

fbshipit-source-id: e8647d665cbe83a3f5429639c6219b50c0912124

monitoring/stats_history_test.cc

@@ -270,10 +270,10 @@ TEST_F(StatsHistoryTest, InMemoryStatsHistoryPurging) {
   }
   size_t stats_history_size = dbfull()->TEST_EstimateInMemoryStatsHistorySize();
   ASSERT_GE(slice_count, 9);
-  ASSERT_GE(stats_history_size, 12000);
+  ASSERT_GE(stats_history_size, 13000);
-  // capping memory cost at 12000 bytes since one slice is around 10000~12000
+  // capping memory cost at 13000 bytes since one slice is around 10000~13000
-  ASSERT_OK(dbfull()->SetDBOptions({{"stats_history_buffer_size", "12000"}}));
+  ASSERT_OK(dbfull()->SetDBOptions({{"stats_history_buffer_size", "13000"}}));
-  ASSERT_EQ(12000, dbfull()->GetDBOptions().stats_history_buffer_size);
+  ASSERT_EQ(13000, dbfull()->GetDBOptions().stats_history_buffer_size);
   // Wait for stats persist to finish
   for (; mock_time < 20; ++mock_time) {
     dbfull()->TEST_WaitForPersistStatsRun(
@@ -292,7 +292,7 @@ TEST_F(StatsHistoryTest, InMemoryStatsHistoryPurging) {
       dbfull()->TEST_EstimateInMemoryStatsHistorySize();
   // only one slice can fit under the new stats_history_buffer_size
   ASSERT_LT(slice_count, 2);
-  ASSERT_TRUE(stats_history_size_reopen < 12000 &&
+  ASSERT_TRUE(stats_history_size_reopen < 13000 &&
               stats_history_size_reopen > 0);
   ASSERT_TRUE(stats_count_reopen < stats_count && stats_count_reopen > 0);
   Close();

table/table_test.cc

@@ -1120,6 +1120,7 @@ class BlockBasedTableTest
       const std::vector<BlockCacheTraceRecord>& expected_records) {
     c->block_cache_tracer_.EndTrace();
 
+    {
       std::unique_ptr<TraceReader> trace_reader;
       Status s =
           NewFileTraceReader(env_, EnvOptions(), trace_file_path_, &trace_reader);
@@ -1165,6 +1166,7 @@ class BlockBasedTableTest
         index++;
       }
       EXPECT_EQ(index, expected_records.size());
+    }
     EXPECT_OK(env_->DeleteFile(trace_file_path_));
     EXPECT_OK(env_->DeleteDir(test_path_));
   }