Server bug fix: Include CAP_SETGID so it does not run as root
* debian/mandos.postinst (configure): If old version was 1.7.4-1 or 1.7.4-1~bpo8+1, fix situation where clients.pickle file is owned by root. * mandos (main): Print debug info about setuid() and setgid() * mandos.service ([Service]/CapabilityBoundingSet): Add "CAP_KILL CAP_SETGID"; the latter is needed for setgid() to be allowed.