pending changes: allow skipping cloud-init

pending changes: allow skipping cloud-init

in case of remote migration, we use the `update_vm_api` helper for
checking permissions on the incoming config. this would also cause an
incoming cloud-init image to be overwritten, since the VM is not running
yet at this point.

provide a parameter which can be set by an incoming *remote* migration
to avoid having inconsistent cloud init images on the source and target
side.

Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>