Don't work with inline_entity_form

Reproduce steps:

1. Install commerce and commerce_product module.
2. Create an product attribute "size" /admin/commerce/product-attributes and set element type as "Select list"
3. Set commerce_product_variation's size field form widget as Select boxes（Single value).
4. Create a product(Every thing works fine in this step).
5. Edit last step's product, and add new variation. the size don't work, after open chrome's inspect and click Console, we can see js error
   

This error caused by the wrong loading order of js file, the select2.full.min.js and select2boxes.js is the last two loaded js file.
This is the relevant issue https://stackoverflow.com/questions/20034522/select2-is-not-a-function