* etc/emacs.service (ExecStart): Make Emacs exit from systemd work
better (bug#45181).
The problem here is the exit code 15, which emacs will return *only* if
it has received SIGTERM. I believe what's happening here is that
emacsclient will call kill-emacs but not wait until the emacs server
has properly shut down. However, it's supposed to wait for the shutdown
as an "ExecStop" command according to "man systemd.service". So since
the process is still alive when emacsclient comes back, systemd will
still issue SIGTERM, making emacs return 15 (maybe after calling kill-
emacs again?!).