This caused problems when users then tried to action the pending
install, where it would no longer have enough information to install the
app. Although it may be technically possible to keep enough information
around in memory to make the app installable, but it is not worth the
effort. If a user intentionally disables a repo, we should no longer be
responsible for keeping information about its apps around.
Fixes#995.
f3c48f8d6b