Package downloading should use normal package listing if user is authenticated as admin

[sdemos]

If a user is authenticating using a CoreUpdate administrator account when using updateservicectl, they should be able to download any packages that are on the server using updateservicectl pkg download, and not just the ones that are considered "public" by the PublicPackagesList api call (which currently are any packages associated with an application that has at least one public channel).

This particularly affects people running private versions of CoreUpdate with no public channels, or ones that only pull public channels from an upstream CoreUpdate (upstream channels are private and can't be configured otherwise). In this case, they won't have any public channels, which means that they won't be able to download any packages associated with that application.

[sym3tri]

good point