Filter the list of license types on the initial variation edit form load

Problem/Motivation

If you have multiple license types on a site, when you configure your product variation type, you get to specify which license types should be supported by the variation type. However, when the variation edit form is first loaded, it's showing all options (or at least more than it should), though once you select a valid one, the list gets filtered correctly.

Steps to reproduce

1. Install Commerce Kickstart.
2. Define a Membership product and product variation type.
3. Restrict the variation type to only support role licenses.
4. Create a new product of that type, choosing "Save and add variations."
5. Add a variation and observe that both File and Role licenses are present in the select list.
6. Select a Role license and observe that the options change to remove File from the options.