11.04 logout menu says reboot required before 11.10 upgrade finishes

[Ryan Thompson]

I am currently halfway through the 11.04 to 11.10 upgrade process, and I just noticed that the power menu in the top right is colored red, and has the "Restart to complete update" option. This is bad, because if someone didn't know better, they might take that suggestion and try to reboot while the upgrade process is still going on, possibly leaving their system in a bad half-upgraded unbootable state. It seems that there should be a way for programs to inhibit the "Restart to complete update" option (or even inhibit all reboot/shutdown/sleep options), and that the upgrade tool should use this inhibition method.