This is stright from VMware Engineering :
"At the current stage: Upgrade from 1.5.2 to 5.1.0 or 5.1.1 is not supported. The upgrade from 1.5.2 to upcoming 5.1.2 will be supported though. The target GA date for VCD 5.1.2 is late April this year."
Don't Upgrade your vCloud 1.5.2 ... like I just did otherwise your dead in the water.
I m currently demanding a workaround since none of this was mentioned in the installation and upgrade documentation of vCloud 5.1.1
Matrix Attached