Packages: always add collections to group/package cache

This fixes cases where the collection itself would not be cached
because a host had no sources, or multiple sources of different types;
we still want to cache package group results and package sets (both of
which will be empty).
Viz: distinguish categories from hosts
Viz: exclude duplicate bundles for a given host
Viz: include clients that should be included, not vice-versa
Revert "Probes: Fix failing nosetests"

This reverts commit 4f745cc2731f7035f02566ba8bc1a0e9ae1b1a71.

This breaks handling of unicode on python 2.
Probes: Fix unicode probe handling

Signed-off-by: Sol Jerome <sol.jerome@gmail.com>