Disable sst_file_manager in stress testing backup restore (#7384)

Summary:
This is potentially the cause of failures:

    Failure in Destroy restore dir with: IO error: file rmdir: /dev/shm/rocksdb/rocksdb_crashtest_whitebox/.restore13: Directory not empty

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7384

Test Plan: smoke test blackbox_crash_test

Reviewed By: jay-zhuang

Differential Revision: D23685087

Pulled By: pdillinger

fbshipit-source-id: 55f62e9853ce84be1d5ca7d856de867f0f2596ee

db_stress_tool/db_stress_test_base.cc

@@ -1318,6 +1318,8 @@ Status StressTest::TestBackupRestore(
   if (s.ok() && !FLAGS_use_txn && !FLAGS_use_blob_db) {
     Options restore_options(options_);
     restore_options.listeners.clear();
+    // Avoid dangling/shared file descriptors, for reliable destroy
+    restore_options.sst_file_manager = nullptr;
     std::vector<ColumnFamilyDescriptor> cf_descriptors;
     // TODO(ajkr): `column_family_names_` is not safe to access here when
     // `clear_column_family_one_in != 0`. But we can't easily switch to