daemon: re-enable SIGWINCH without setsid
This allows systemd users to use SIGWINCH to temporarily
(and gracefully) stop an instance of a service without
doing a code reload to bring it back up:
# start temporary new service code
systemctl start public-inbox-nntpd@2.service
# momentarily paralyze original service
systemctl kill -s WINCH public-inbox-nntpd@1.service
if new_code_at_2_sucks
then
# restart original workers
systemctl kill -s HUP public-inbox-nntpd@1.service
else # new is better than old, replace original instance
systemctl restart public-inbox-nntpd@1.service
fi
# cleanup the temporary service
systemctl stop public-inbox-nntpd@2.service
This partially reverts commit
73d274e83b7d300f31e0cc1ceeacbf73c6c2a1e4
("daemon: disable SIGWINCH unless explicitly daemonized")