Remove sync point from Block destructor (#4370)

Summary:
AddressSanitizer: heap-use-after-free in std::__atomic_base<bool>::load(std::memory_order) const
==1798517==ABORTING
```
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4370

Differential Revision: D9844146

Pulled By: sagar0

fbshipit-source-id: 18a2970b1d504b4f6c8fb04857f26e0f32124dd1

db/db_test2.cc

@@ -2649,7 +2649,7 @@ TEST_F(DBTest2, PinnableSliceAndMmapReads) {
 #endif
 }
 
-TEST_F(DBTest2, IteratorPinnedMemory) {
+TEST_F(DBTest2, DISABLED_IteratorPinnedMemory) {
   Options options = CurrentOptions();
   options.create_if_missing = true;
   options.statistics = rocksdb::CreateDBStatistics();

table/block.cc

@@ -762,7 +762,11 @@ BlockBasedTableOptions::DataBlockIndexType Block::IndexType() const {
   return index_type;
 }
 
-Block::~Block() { TEST_SYNC_POINT("Block::~Block"); }
+Block::~Block() {
+  // This sync point can be re-enabled once the right order for global static
+  // initialization/destruction across compilation units is determined.
+  // TEST_SYNC_POINT("Block::~Block");
+}
 
 Block::Block(BlockContents&& contents, SequenceNumber _global_seqno,
              size_t read_amp_bytes_per_bit, Statistics* statistics)