Add missing license header to ironic-ilo-virtualmedia-driver

The spec template has a license header, and all approved specs contain
this header, save for one.

This patch adds the missing CC-BY-UL license header to
ironic-ilo-virtualmedia-driver

A future patch should add a test for this.

Change-Id: I112003ad198b55decc5e6ab8585314433f836cfb