tests: make test cleanup more defensive - qubes.xml load failure
tests: make test cleanup more defensive - qubes.xml load failure

If qubes.xml doesn't even load, remove it anyway and clean up the VMs
the hard way.

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