Filter out QEMU DVD-ROM from disk_util_devices
Filter out QEMU DVD-ROM from disk_util_devices

This commit filters out QEMU DVD-ROM devices from the
disk_util_devices list, in turn removing them from
being included in alarm criteria for the disk_utilisation
plugin.

Connects https://github.com/rcbops/rpc-openstack/issues/2255

briancurtin/rpc-maas,npawelek/rpc-maas,cloudnull/rpc-maas,cloudnull/rpc-maas,cfarquhar/rpc-maas,cfarquhar/rpc-maas,cfarquhar/rpc-maas,npawelek/rpc-maas,briancurtin/rpc-maas,cloudnull/rpc-maas,briancurtin/rpc-maas,npawelek/rpc-maas