Merge pull request #13866 from keszybz/nspawn-restarts

Make 'machinectl reboot' functional

diff --cc src/core/service.c
Simple merge

diff --cc src/machine/machine-dbus.c
Simple merge

diff --cc src/nspawn/nspawn-register.c
Simple merge

diff --cc src/nspawn/nspawn.c
Simple merge