Don't list apps that are disabled by the system

This is to make sure that apps that were disabled for some reason
such as inappropriateness for a locale or for a specific device, don't
show up as available to enable for a restricted profile.

But in the case that the app was already enabled for the target profile,
show it in the list so that it can be disabled if necessary.

Bug: 10229133
Change-Id: I3c19edb7364cea42d95b619781e0326543b9a1cf