internal/oem: mask services on brightbox and openstack
internal/oem: mask services on brightbox and openstack

This commit masks user-configdrive.service and user-configvirtfs.service
on brightbox and openstack, because the cloud config that was used on
these platforms before the migration to Ignition masked them.

AlexNPavel/ignition,dgonyeo/ignition,ajeddeloh/ignition,dgonyeo/ignition,ajeddeloh/ignition,coreos/ignition,coreos/ignition,AlexNPavel/ignition,AlexNPavel/ignition,coreos/ignition,dgonyeo/ignition,ajeddeloh/ignition