Recent updates to Djblet's ListEditWidget has caused Reviewboard's OAuth App

API to fail on POST and PUT requests because the OAuth App API wraps the OAuth

ApplicationChangeForm, which relies on the legacy behavior of the 

ListEditWidget for its redirect_uris field. The legacy behavior of the

widget is to take in a string and split it into a list, as opposed to the modern

behavior of taking in a list. The redirect_uris field must be stored as a

string of space-separated URIs (this is required by 

oauth2_provider.models.AbstractApplication). Usually the ListEditWidget and

corresponding ListEditField will take care of converting string inputs into

lists, but this does not happen properly in cases where the widget is not

rendered.
This change makes the ApplicationChangeForm take care of converting the

redirect_uris field data into a list to ensure that the redirect_uris data

is properly passed to the widget's methods and saved to the form in cases

where the widget is not rendered.

Ran OAuth Unit tests.
Ran OAuth App API Unit tests.
Manually tested the OAuth Application form in the admin settings UI.