Back out r505456. sshguard 2.4.0 misbehaves

SSHGuard has always exited cleanly on FreeBSD. In 2.4.0, sshguard fixed that.
It is impossible to terminate sshguard without manually killing each process.

So, apologies to everyone who's already updated, but you'll have to manually
kill all the processes:

pkill -f sshguard
pkill -f sshg-
pkill -f tail
rm /var/run/sshguard.pid

So, back this out while awaiting upstream fix.

PR: 238458