support separate registry/api packages

on Debian plattforms there are separate packages
for glance registry and glance api. This allows
you to install api/registry on different servers.

If the packages for registry and api are the same,
(as it is the case for RedHat plattform)
the package is installed in ::glance class.
If the packages differs (as for Debian plattform),
installation of packages is done in
registry/api classes.

Additionaly this patch adds a test for unsupported
plattforms.

Change-Id: I8d4b74e8c8ad2dd7e6e2ad175326f36ff818c108
Merge git://github.com/puppetlabs/puppetlabs-glance