Fix VersionStorageInfo::EstimateLiveDataSize seg fault

Summary:
`HandleEstimateLiveDataSize`'s `need_out_of_mutex` is true
402b7aa07f/db/internal_stats.cc (L412-L413)
so , is will ref a `SuperVersion`
402b7aa07f/db/db_impl.cc (L1896-L1908)
so , the param `version` of `InternalStats::HandleEstimateLiveDataSize` is safe , but `cfd_->current()` is not safe !
402b7aa07f/db/internal_stats.cc (L790-L795)

the `cfd_->current()` maybe invalid ...

here's mongo-rocks crash backtrace
```
 mongod(mongo::printStackTrace(std::basic_ostream<char, std::char_traits<char> >&)+0x41) [0x7fe3a3137c51]
 mongod(+0x2152E89) [0x7fe3a3136e89]
 mongod(+0x21534F6) [0x7fe3a31374f6]
 libpthread.so.0(+0xF5E0) [0x7fe39f5e45e0]
 mongod(rocksdb::InternalKeyComparator::Compare(rocksdb::Slice const&, rocksdb::Slice const&) const+0x17) [0x7fe3a22375a7]
 mongod(rocksdb::VersionStorageInfo::EstimateLiveDataSize() const+0x3AA) [0x7fe3a228daba]
 mongod(rocksdb::InternalStats::HandleEstimateLiveDataSize(unsigned long*, rocksdb::DBImpl*, rocksdb::Version*)+0x20) [0x7fe3a2250d70]
 mongod(rocksdb::DBImpl::GetIntPropertyInternal(rocksdb::ColumnFamilyData*, rocksdb::DBPropertyInfo const&, bool, unsigned long*)+0xEF) [0x7fe3a21e3dbf]
```
Closes https://github.com/facebook/rocksdb/pull/3912

Differential Revision: D8179944

Pulled By: yiwu-arbug

fbshipit-source-id: 26f314a8f98f4c2dc4348745d759f26f0e8d95e1

db/internal_stats.cc

@@ -788,8 +788,8 @@ bool InternalStats::HandleEstimateTableReadersMem(uint64_t* value,
 }
 
 bool InternalStats::HandleEstimateLiveDataSize(uint64_t* value, DBImpl* /*db*/,
-                                               Version* /*version*/) {
-  const auto* vstorage = cfd_->current()->storage_info();
+                                               Version* version) {
+  const auto* vstorage = version->storage_info();
   *value = vstorage->EstimateLiveDataSize();
   return true;
 }