Fix cyclic references in SDR
Fix cyclic references in SDR

SDR and SDR entries had a cyclic reference to ipmicmd.  Weaken
it so that it won't cause issues (whether real or just
complicating output of guppy)

Change-Id: Iad9c9726026f46c9a104c4a7464fad9b17d336ea

stackforge/pyghmi,openstack/pyghmi,openstack/pyghmi