disable privilege-drop verification by default as fakeroot trips over it

disable privilege-drop verification by default as fakeroot trips over it

Dropping privileges is an involved process for code and system alike so
ideally we want to verify that all the work wasn't in vain. Stuff
designed to sidestep the usual privilege checks like fakeroot (and its
many alternatives) have their problem with this through, partly through
missing wrapping (#806521), partly as e.g. regaining root from an
unprivileged user is in their design. This commit therefore disables
most of these checks by default so that apt runs fine again in a
fakeroot environment.

Closes: 806475