how sudo handles $HOME

[Dan Streetman]

in Ubuntu, sudo retains the calling user's $HOME

this is different from upstream sudo as well as all other UNIXes and
even the sudo documentation we provide.  Should we remove our custom
patch that adds this behavior?

for reference and more details on downsides of our current sudo behavior, see:
https://bugs.launchpad.net/ubuntu/+source/sudo/+bug/1556302

Note that I have kind-of hijacked the bug, as I believe the issue is
larger than the python-based example in that bug.

Also as I commented in that bug, I do not recommend changing the
behavior for existing releases.  But I do think we should change the
behavior starting in Eoan and future releases.