r/collectd: Ignore efivarfs mounts

There's not much point in alerting based on the utilization of this
virtual filesystem.

roles/collectd/defaults/main.yml

@@ -4,6 +4,7 @@ collectd_network_servers: []
 collectd_network_listen: []
 collectd_df_ignore_mountpoint: []
 collectd_df_ignore_fstype:
+- efivarfs
 - overlay
 
 collectd_plugins: {}