Without this, even installed packages still get an "Install" button.
Fixes#14821.
This was implemented by adding BPackageRoster::IsPackageActive. I decided to
have this take a location since GetActivePackages also did, but as noted in my
TODO comment, I think this is awkward.
It would also be nice to show the user they have a different version of a
particular package, but that would require some changes to IsPackageActive.
Change-Id: Iab0d35eb6b671a17711b0214b15164d296927e5a
Reviewed-on: https://review.haiku-os.org/c/1694
Reviewed-by: Stephan Aßmus <superstippi@gmx.de>
b711002d34