gettys are nowadays mostly autospawned and hence usually subject to
being shut down on isolate requests, since they are no dependency of any
other unit. This is a bad idea if the user isolates between
multi-user.graphical and graphical.target, hence exclude them from the
isolation.

This has the effect that gettys no longer cleaned up when
emergency.target is isolated, which might actualy be considered a
feature, even though it is a change from previous behaviour...

Note that the one getty that really matters (the one on tty1) is still
removed when isolating to emergency.target since it conflicts with
emergency.service.