When a sigchld is received from an alien child, main_pid is set to
0 then service_enter_running calls main_pid_good to check if the
child is running. This incorrectly returned true because
kill(main_pid, 0) would return >= 0.
This fixes an error where a service would die and the cgroup would
become empty but the service would still report as active (running).
/* If it's an alien child let's check if it is still
* alive ... */
- if (s->main_pid_alien)
+ if (s->main_pid_alien && s->main_pid > 0)
return kill(s->main_pid, 0) >= 0 || errno != ESRCH;
/* .. otherwise assume we'll get a SIGCHLD for it,