Replace the statefulset if it cannot be updated. (#18)

Updates to statefulset spec for fields other than 'replicas' and
containers' are forbidden. However, it is possible to delete the old
statefulset without deleting its pods and create the new one, using the
changed specs. The new statefulset shall pick up the orphaned pods.

Change the statefulset's comparison to return the combined effect of
all checks, not just the first non-matching field.