hosts: Update mtrcs0 FQDN

I moved the metrics Pi from the red network to the blue network.  I
started to get uncormfortable with the firewall changes that were
required to host a service on the red network.  I think it makes the
most sense to define the red network as egress only.

host_vars/mtrcs0.pyrocufflink.blue.yml

@@ -0,0 +1,5 @@
+host_uses_firewalld: false
+collectd_unixsock_plugin: false
+
+collectd_plugins:
+  thermal: true