Is the PostgreSQL database really necessary to install the Virtual Server Agent?
I can check this further for you if you havent already discovered it for yourself.
Could you confirm the Commvault Version and type of Hypervisor you want to protect?
V10/Commvault Next Generation Platform?
We use the V10/Commvault Simpana as Backupsystem and the Linux version of VMware vCenter Server Appliance 6.0 to manage the VMs