Upstream switched to a different type of ipset table, whereas we
create ipset in post-start which overrides upstream, and renders
sshguard ineffective.
Remove ipset creation from post-start, and let it get automatically
by upstream script (sshg-fw-ipset) as part of startup
1. Allow syslog identifiers with special characters
2. Do not write a pid file as we are running in foreground anyway
3. Clean up the module for readability
Without this, when deploying using nixops, restarting sshguard would make
nixops show an error about restarting the service although the service is
actually being restarted.
