Skip some activation key tests due to BZ 1127335

Elasticsearch is used to index new activation keys when they are created.
Unfortunately, elasticsearch cannot keep up when the system is under heavy load.
Make `ActivationKey.read_raw` only re-try a read upon receiving a 404 if
bugzilla bug 1127335 is open. Add the the `skip_if_bug_open` decorator to all
appropriate tests in module `test_activationkey`.
I've added this decorator to every test that calls `ActivationKey.read_json`, as BZ 1127335 manifests itself every time an activation key is created and is subsequently read.