This changes the equivalence class hashing function to use as inputs all
the Pod fields which are read by FitPredicates. Before we used a
combination of OwnerReference and PersistentVolumeClaim info, which was
a close approximation. The new method ensures that hashing remains
correct regardless of controller behavior.
The PVCSet field can be removed from equivalencePod because it is
implicitly included in the Volume list.
Tests are now broken.
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