Add the comment about cyclic reference
Add the comment about cyclic reference

Change-Id: If42c0c1d5fc2a3d6d1109c960344254868d490aa

vganapath/rally,gluke77/rally,gluke77/rally,vganapath/rally,openstack/rally,eayunstack/rally,yeming233/rally,openstack/rally,gluke77/rally,eonpatapon/rally,openstack/rally,yeming233/rally,eayunstack/rally,eayunstack/rally,vganapath/rally,vganapath/rally,gluke77/rally,eonpatapon/rally,openstack/rally