Go through normal where logic in destroy with locking

Building the Arel AST, and manipulating the relation manually like this
is prone to errors and breakage as implementation details change from
underneath it.

activerecord/lib/active_record/locking/optimistic.rb

@@ -125,12 +125,8 @@ def relation_for_destroy
           relation = super
 
           if locking_enabled?
-            column_name = self.class.locking_column
-            column      = self.class.columns_hash[column_name]
-            substitute  = self.class.connection.substitute_at(column)
-
-            relation = relation.where(self.class.arel_table[column_name].eq(substitute))
-            relation.bind_values << [column, self[column_name].to_i]
+            locking_column = self.class.locking_column
+            relation = relation.where(locking_column => _read_attribute(locking_column))
           end
 
           relation