Allow hypervisor types to also consume system subscriptions.

This removes some unused code. I originally thought pre_global was not used but it
is, and it remains in there. I am not sure why the ConsumerResourceEntitlementRulesTest.java
change was required but it seems a fair one.
Add another test to ensure that systems can not consumer hypervisor subscriptions
Fixed typo based on wpoteats code review
Merge pull request #298 from candlepin/bkearney/hypervisor-as-system

Allow hypervisor types to also consume system subscriptions.