Fix SstFileManager uninitialized data member

Summary: I have introduced max_allowed_space_ but did not initialize it

Test Plan: make check

Reviewers: sdong, yhchiang, anthony

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D54357

util/sst_file_manager_impl.cc

@@ -20,6 +20,7 @@ SstFileManagerImpl::SstFileManagerImpl(Env* env, std::shared_ptr<Logger> logger,
     : env_(env),
       logger_(logger),
       total_files_size_(0),
+      max_allowed_space_(0),
       delete_scheduler_(env, trash_dir, rate_bytes_per_sec, logger.get(),
                         this) {}