sloppy apt remove can crowbar product

Doing an "apt remove maas" (instead of "apt autoremove maas") can sometimes lead to a situation where remove completes, but processes are still running. Reboot won't fix it, and then doing an "autoremove" completes successfully, but "apt-get purge maas*" hangs up complaining about running processes.

Surgically killing the highest postgresql process in the tree seems to clear this, so that user can follow codylab's recommended uninstall process here:

https://discourse.maas.io/t/reinstallation/343/2

This is intermittent for some reason, tried 3 times and encountered it once.

Directory /var/log/maas is present, but empty.
dpkg -l '*maas*'|cat reports "no packages found matching *maas*"

Created this bug by typing:

sudo apt remove maas

then doing:

ps -ef | grep maas.

(Editorial: Since this is an intermittent bug and admittedly sloppy use of apt, this could be fixed with doc if desired. I see the notes on not suggesting fixes, but I happen to be the doc guy for this product, so....)