Fix qouting of attributes in the update part of upsert query for mysql. Closes #2668

lib/dialects/mysql/query-generator.js

@@ -172,8 +172,9 @@ module.exports = (function() {
       options.onDuplicate = 'UPDATE ';
       options.onDuplicate = 'UPDATE ';
 
 
       options.onDuplicate += Object.keys(updateValues).map(function (key) {
       options.onDuplicate += Object.keys(updateValues).map(function (key) {
+        key = this.quoteIdentifier(key);
         return key + '=VALUES(' + key +')';
         return key + '=VALUES(' + key +')';
-      }).join(', ');
+      }, this).join(', ');
 
 
       return this.insertQuery(tableName, insertValues, rawAttributes, options);
       return this.insertQuery(tableName, insertValues, rawAttributes, options);
     },
     },