I've heard of someone having this issue in the past but opened an SR to get it resolved. When 6.0 is upgraded to vCSA 6.5, UID 1006 belongs to user "content-library". If you have a clone of this vCenter (or if it's a lab) and you want to experiment on changing the UID, I might try that. The key will be finding all files that had the old UID and changing those since these users don't have a /home. If you want to try that out, look for those files first.
find / -user vdcs
Assign a temporary UID to vdcs with usermod -u xxxx vdcs where "xxxx" is some UID not taken. This will give you all UIDs assigned to known users and so is easier to not create a collision:
awk -F: '{printf "%s:%s\n",$1,$3}' /etc/passwd
Then you'll have to change all files ownership from when vdcs had UID 1007 to its new UID of 1006.
find / -user 1007 -exec chown -h vdcs {}
I haven't tried this myself although I would if I still had a vCSA 6.0 laying around. If you do test this out, you may need to stop all services (service-control --stop --all) before changing UIDs as some daemons will panic the next time they fetch binaries from disk.
I don't know if this will be of any help, but if you are able to test it out it may be worth a shot. FWIW I guess...