Have exact same problem only from vCenter Appliance version 5.0.0.3324 Build 472350 update to 5.0.0.8512 Build 1302764 (Error while running post install scripts).
Attempted ODBC configuration for Embedded with same error cannot connect to DB.
Did you end up resolving the issue?
I'm starting to think it will be easier removing vm's from inventory installing new version of vCenter Applicance and reconnecting hosts to be managed by new server. I didn't have any special setup in vCenter so it doesn't hold any special configuration information that needs to be restored.
Let me know how you resolved your problem much appreciated.