Prevent change of gid of debian-tor user breaking automatic upgrades. (Closes: #15695)
As outlined in
a774ba2aba7012f3f5bc630b0f3dab8ac696dbd7, since the
virtualbox 5.2.8-dfsg-7 upload the virtualbox-guest-utils package depends
on virtualbox-guest-dkms which in-turn creates a "vboxsf" group later than
before.
This results in the resulting debian-tor group ID being assigned a
different number due to change of relative ordering and, accordingly,
breaks automatic upgrades.
We therefore assign a number of groups, fresh, unreserved group IDs to
avoid collisions.