Default values for Commerce content only work for selected language when content is created

Description

Fix for making default values for Commerce content work for selected languages.

Steps to reproduce:

1. On the Commerce Quicksilver sample site, make sure there are multiple languages enabled for catalog content (en, sv - where en is master and selected language).
2. Create some content which inherits from NodeContent like:

public class TestContent : NodeContent 
{
     [CultureSpecific] 
     public virtual string Text {get;set;}

     public override voide SetDefaultValues(ContentType contentType)
     {   
        Text = "Some text";
        base.SetDefaultValues(contentType);   
     }
}

          3. Create TestContent in catalog.

Expected:

Should set default value for all language versions (en, sv).

Actual:

Only sets it for the selected language (en) when creating the content (not for sv).