Fix db_stress failure (#8632)

Summary:
FaultInjectionTestFS injects error in Rename operation. Because
of injected error, info.log fails to be created if rename  returns error and info_log is set to nullptr which leads to this assertion

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8632

Test Plan: run the db_stress job locally

Reviewed By: ajkr

Differential Revision: D30167387

Pulled By: akankshamahajan15

fbshipit-source-id: 8d08c4c33e8f0cabd368bbb498d21b9de0660067

db_stress_tool/db_stress_test_base.cc

@@ -1366,7 +1366,6 @@ Status StressTest::TestBackupRestore(
   BackupableDBOptions backup_opts(backup_dir);
   // For debugging, get info_log from live options
   backup_opts.info_log = db_->GetDBOptions().info_log.get();
-  assert(backup_opts.info_log);
   if (thread->rand.OneIn(10)) {
     backup_opts.share_table_files = false;
   } else {