Autobind correct quantities for instance based subs.

Physical systems need 2 entitlements for every socket pair.

Virtual systems only ever need 1 entitlement regardless of socket/vcpu
count.

Needs to be calculated by adjusting the value of what each entitlement
actually provides, not by adjusting the sockets on the systems
themselves.
Add tests for new host rectricted stacking behaviour.
Do not enforce attributes in some situations.

Instead of using -1's or infinity, disable enforcement of
sockets/ram/cores in some situations.

Currently just used for instance based subscriptions when a guest is
binding, or for guests binding to host restricted sub-pools.
Add a no-attribute stack edge case test.
Instance based autobind cleanup.
Add tests for modified host restricted stacking.

Guests binding to host restricted pools are now exempt from all stacking
attribute enforcement, only a quantity of 1 is required.

This was implemented in shared code during the autobind work, so it
seems no changes are necessary.
Change assumption about default quantity during autobind.
Move coverage adjustment inside a more generic method.
Merge pull request #241 from candlepin/dgoodwin/instancebased

Dgoodwin/instancebased