const fix for the rest of the files under storage/rocksdb after rebase (

percona#480) (percona#480)

Summary:
This is the last pull request for the const fix of all the files under storage/rocksdb.

The changes will improve the robustness of the code and make it easier for refactoring in the future.
Closes facebook/mysql-5.6#480

Differential Revision: D4349370

Pulled By: sidigit1205

storage/rocksdb/event_listener.cc

@@ -39,7 +39,7 @@ extract_index_stats(
 ) {
   std::vector<Rdb_index_stats> ret;
   for (auto fn : files) {
-    auto it = props.find(fn);
+    const auto it = props.find(fn);
     DBUG_ASSERT(it != props.end());
     std::vector<Rdb_index_stats> stats;
     Rdb_tbl_prop_coll::read_stats_from_tbl_props(it->second, &stats);
@@ -52,7 +52,8 @@ void Rdb_event_listener::update_index_stats(
   const rocksdb::TableProperties& props
 ) {
   DBUG_ASSERT(m_ddl_manager != nullptr);
-  auto tbl_props = std::make_shared<const rocksdb::TableProperties>(props);
+  const auto tbl_props =
+    std::make_shared<const rocksdb::TableProperties>(props);
 
   std::vector<Rdb_index_stats> stats;
   Rdb_tbl_prop_coll::read_stats_from_tbl_props(tbl_props, &stats);

storage/rocksdb/event_listener.h

@@ -27,12 +27,12 @@ class Rdb_event_listener : public rocksdb::EventListener
   Rdb_event_listener(const Rdb_event_listener&) = delete;
   Rdb_event_listener& operator=(const Rdb_event_listener&) = delete;
 
-  explicit Rdb_event_listener(Rdb_ddl_manager* ddl_manager) :
+  explicit Rdb_event_listener(Rdb_ddl_manager* const ddl_manager) :
       m_ddl_manager(ddl_manager) {
   }
 
   void OnCompactionCompleted(
-    rocksdb::DB *db, const rocksdb::CompactionJobInfo& ci) override;
+    rocksdb::DB* db, const rocksdb::CompactionJobInfo& ci) override;
   void OnFlushCompleted(
     rocksdb::DB* db, const rocksdb::FlushJobInfo& flush_job_info) override;
   void OnExternalFileIngested(