backup: allow backup running VMs
backup: allow backup running VMs

Since we have LVM by default, it is possible to backup VMs while they
are running. For now it will include its state from before startup, but
later we may implement some other logic (a snapshot of running VM).

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