Ya I have looked high and low for a solution. Just as Peter mentioned, the reservation pools in vSphere and the vCloud settings do not match.I have a case open currently and the current recommended fix is to upgrade to 5.1.2.
The concern I have expressed is if the reservations are not set within vSphere, what will happen if I upgrade, the issue gets resolved and now I have reservations set in vSphere. HA admission control could scream as the slot sizes have changed and thus HA may not operate as expected.
This is a pretty scary bug that on the surface has no major effect, but the potential is massive. Obviously a quick short term fix is to manually change the HA slot sizes but that is not a long tern fix.
I welcome you to look at my open SR. The more eyes the better for those of us that are experiencing this issue. When thinking about the consequences of applying a reservation to 1000's of Vms, the simple fix that VMware has been recommending isn't as simple as one would think, and actually might need to be rectified prior to upgrading.