RepositoryForm was setting some initial values for the form from an

instance a bit too late in the process, causing our hosting_type field

to be set after it was accessed. While this didn't show any regressions

on Django 1.6 (though it's possible there are some), it outright fails

on Django 1.11.
This change fixes the logic to set all the initial state earlier and in

one place, so it's more clear where similar code in the future should

go. It also adds comments to the methods responsible for setting the

state, indicating some requirements as to what state those functions are

allowed to access.
This all exposed an issue where an SCMTool form was being populated with

data when a hosting service was set. This doesn't cause any real-world

problems, but it was incorrect, and a bad unit test wasn't checking this

resulting state correctly. The above fix also fixed this, which broked

the bad unit test.
Both the unit test and another that was checking form values in a

non-future-proof way have been fixed.

Unit tests passed here and on release-4.0.x (with Django 1.11).