Draft: Revert "Ensure that dh_installtmpfiles is run before dh_installsysusers", reproducing #1070119

The sysusers.d(5) snippet must be handled before tmpfiles.d(5), otherwise the system user that is meant to own the directory will not yet exist; so I think #1070119 needs to be resolved some other way.

This reverts commit 84909192.