Improved macspoof hook README following user request

Change-Id: I52963e5a344ba12a97906a9d8ed8f22cc2919718
Signed-off-by: Assaf Muller <amuller@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/22760
Reviewed-by: Dan Kenigsberg <danken@redhat.com>