vm/qubesvm: remove pool_name property
vm/qubesvm: remove pool_name property

It isn't used anywhere - in core3 each storage volume have pool assigned
- which may be different for each volume.

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