Cleanupped P_001P001ModelTests and fixed testModelWithoutDeallocSwizzleUnswizzle

Created ivars (and `setup`'d them) to provide concise and flexible references to P_001P001ModelTestsModel and P_001P001ModelTestsModelWithoutDealloc, respectively.

Second, fixed `testModelWithoutDeallocSwizzleUnswizzle` to test `aModelWithoutDeallocClass`, not `aModelClass`.