fix #3861: migrate: fix live migration when cloud-init changes storage

fix #3861: migrate: fix live migration when cloud-init changes storage

Generalizes fd95d780 ("migrate: send updated TPM state volid to target
node") to also handle other offline migrated disks appearing in the
VM config, which currently should only be cloud-init.

Breaks migration new -> old under similar (edge-case-)conditions as
fd95d780 did.

Keep sending the 'tpmstate0' STDIN parameter to avoid breaking new ->
old in the scenario fd95d780 fixed.

Keep parsing the vm_start 'tpmstate0' STDIN parameter to avoid
breaking old -> new, and to be able to keep sending it.

Signed-off-by: Fabian Ebner <f.ebner@proxmox.com>