Unittests: Elaborate on the MessageDirector test_range tests.

Add a defined behavior for parts where it was previously ignored pending discussion.
Add note blocks describing alternate behaviors which are not clearly better or worse.
Be more strict with the behavior of some upstream unsubscribes, when it is clearly better.
Bugfix: Satisify unittest changes for MD test_ranges.

Greatly simplifies the upstream range unsubscription.
Allows us more restricted ranges while also reducing computational complexity.