ircd: make check_ircd a critical (paging) icinga check
This would make the existing "check_ircd" check a critical
check which means it would start sending SMS to ops.
This isn't a new check and has been there for a while,
it runs check_ircd from a nagios-plugins package which
is a Perl script that connects to the ircd.
(I248dac3cacb82471cf , I21a3ca32fd425dd20 puppetized a
manual setup from before that afaict)
This change is in reaction to T135948 though the issue
was not actually that no ircd was running but rather that the
irc bot wasn't on the irc server after a restart of the VM and
of course that VMs are freezing which required the restart.
So i'm not 100% sure if this would have been much more helpful,
it would have created pages on restart of the VM.