dom0: Fix qvm-prefs for standalone VM
dom0: Fix qvm-prefs for standalone VM

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