Syslogd should ensure that f_file is a valid file descriptor when
f_type is FILE, CONSOLE, TTY and for a PIPE where f_pid > 0. If the
descriptor is closed/invalid then the type should be set to UNUSED
or the pid should be set to 0.
To this end:
1) Don't close(f->f_file) if we can't send a message to a remote
host because the file descriptor used for remote logging is
stored in finet, not in f->f_file. f->f_file is probably
uninitialised, so I guess we usually end up closing fd 0.
2) Don't close PIPE file descriptors if they are invalid.
3) If the call to p_open fails, don't set the pid.
The OpenBSD patches in this area set f_file to -1 after the fd is
closed and then avoids calling close if f_file < 0. I haven't done
this, but it might be a good idea too.
Inspired by: PR 67139/OpenBSD
1b2d9d1890