Fixes #144

While fixing the issue and adding the test case, i found trwo other issues:
* One in subscriptionBase where cancelling one ADD_ON would trigger cancellation of the others (weird we did not see that before ?)
* One issue in entitlement system where blocking an already blocked entitlement would do the right thing but generate an additional bus event.

An additional test to verify #144 in case there are multiple bundles still need to be written.

Also, tests seemed more flaky-- first iteration of running them failed (beatrix).