This commit simply modernizes the comparisons made in the storage tests
to use `cmp.Diff()` so that pointer comparisons and length checks do not
have to be made by hand. We also get nice diffs in the test output this
way instead of large pasted blobs.
Signed-off-by: Steve Kuznetsov <skuznets@redhat.com>
Kubernetes-commit: dfdd486f09321e9105fa747a8d1ac5a9a2a7a94a