tests: minor fix to revert changes tests, mark as expected failure
tests: minor fix to revert changes tests, mark as expected failure

While the test should be ok now, the functionality itself doesn't work (at
least on file volumes).

marmarek/qubes-core-admin,marmarek/qubes-core-admin,woju/qubes-core-admin,woju/qubes-core-admin,woju/qubes-core-admin,QubesOS/qubes-core-admin,marmarek/qubes-core-admin,QubesOS/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin