Fix missing const for arg of OptionChangeMigration (facebook#14173)

Summary:
Fix missing const for arg of OptionChangeMigration

We switched from std::string to std::string & for API OptionChangeMigration, which caused const qualifier to be lost at call site, which causes compilation failure.

Pull Request resolved: facebook#14173

Test Plan: Unit test

Reviewed By: pdillinger

Differential Revision: D88431457

Pulled By: xingbowang

fbshipit-source-id: a705f3b80cc5ff56dab73aa6a31c940798d8df45

Author: xingbowang

include/rocksdb/utilities/option_change_migration.h

@@ -25,7 +25,7 @@ namespace ROCKSDB_NAMESPACE {
 // with `Options::compaction_options_fifo.max_table_files_size` > 0 can cause
 // the whole DB to be dropped right after migration if the migrated data is
 // larger than `max_table_files_size`
-Status OptionChangeMigration(std::string& dbname, const Options& old_opts,
+Status OptionChangeMigration(const std::string& dbname, const Options& old_opts,
                              const Options& new_opts);
 
 // Multi-CF version: Prepares a database with multiple column families to be

utilities/option_change_migration/option_change_migration.cc

@@ -341,7 +341,7 @@ Status OptionChangeMigration(
   return s;
 }
 
-Status OptionChangeMigration(std::string& dbname, const Options& old_opts,
+Status OptionChangeMigration(const std::string& dbname, const Options& old_opts,
                              const Options& new_opts) {
   DBOptions old_db_opts(old_opts);
   DBOptions new_db_opts(new_opts);