Theme values were not actually being updated via the theme install rake task, because
update_from_remote does not save the theme.
In the admin controller, when updating a theme from remote, we see
theme is saved later in the action
The update_from_remote method sets fields on the
theme, but does not save the theme.
In the rake task, I was assuming that the theme was automatically saved by
update_from_remote', so adding save here is a fix! It is a bit of an interesting paradigm to wait to save theme` outside the update method, but it makes more sense in the context of how the controller uses the method.