broken test for update short path

Sequelize tries to optimize which fields are being updated by
checking previous data values, and determining whether or not
fields should be used in an UPDATE clause. Unfortunately, the
case where NO fields should be used in the clause was never
checked.

test/instance/update.test.js

@@ -93,6 +93,35 @@ describe(Support.getTestDialectTeaser('Instance'), function() {
       });
     });
 
+    it('should succeed in updating when values are unchanged (without timestamps)', function() {
+      var User = this.sequelize.define('User' + config.rand(), {
+        name: DataTypes.STRING,
+        bio: DataTypes.TEXT,
+        email: DataTypes.STRING
+      }, {
+        timestamps: false
+      });
+
+     return User.sync({force: true}).then(function() {
+        return User.create({
+          name: 'snafu',
+          email: 'email'
+        }, {
+          fields: ['name', 'email']
+        }).then(function(user) {
+          return user.update({
+            name: 'snafu',
+            email: 'email'
+          });
+        }).then(function(user) {
+          return user.reload();
+        }).then(function(user) {
+          expect(user.get('name')).to.equal('snafu');
+          expect(user.get('email')).to.equal('email');
+        });
+      });
+    });
+
     it('should only save passed attributes', function () {
       var user = this.User.build();
       return user.save().then(function () {
@@ -379,4 +408,4 @@ describe(Support.getTestDialectTeaser('Instance'), function() {
       });
     });
   });
-});
\ No newline at end of file
+});