core: When adding a VdsGroup Cluster audit 'Cluster' not 'Host cluster'

Change-Id: I040cd914c20eecce54e5a0245e22f2cc24a43a7a
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1016661
Signed-off-by: Mooli Tayer <mtayer@redhat.com>