Wrong argument was passed to Apply_changes_iter::init()

Summary:
Apply_changes_iter::init() function takes "bool is_reverse_arg"
as a first argument, but actually RDBSE_KEYDEF was passed from
ha_rocksdb::setup_index_scan(). So is_reverse_arg was
always true, and RocksDB SE did always reverse index scan,
and it also broke Apply_changes_iter behavior.
This diff passes correct variable (keydef->is_reverse_cf),
and with this fix, I confirmed bug#19 fixed.

Test Plan: mtr --suite=rocksdb, including rocksdb.transaction

Reviewers: sergey.petrunya.9, hermanlee4, maykov, jonahcohen

Reviewed By: jonahcohen

Subscribers: jtolmer

Differential Revision: https://reviews.facebook.net/D31551

storage/rocksdb/ha_rocksdb.cc

@@ -2889,7 +2889,7 @@ void ha_rocksdb::setup_index_scan(RDBSE_KEYDEF *keydef,
       options.snapshot= trx->snapshot;
     rocksdb::Iterator* rocksdb_it= rdb->NewIterator(options, keydef->get_cf());
     scan_it= new Apply_changes_iter;
-    scan_it->init(keydef, &trx->changes, rocksdb_it);
+    scan_it->init(keydef->is_reverse_cf, &trx->changes, rocksdb_it);
   }
 
   /*