expose fluentd metrics also on IPv6

Currently, IPv6 only clusters cannot scrape metrics from fluentd, as fluentd's `bind` default is `0.0.0.0`. Any IPv6 only cluster will fail scrapes.

fluentd currently does not support binding both IPv6 and IPv4 in a single source. Adding a second IPv6 source makes fluentd listen on both IPv4 and IPv6, allowing scrapes universally.

Fixes #1835

pkg/resources/fluentd/config.go

@@ -63,6 +63,15 @@ var fluentdInputTemplate = `
     metrics_path {{ .Monitor.Path }}
 {{- end }}
 </source>
+<source>
+    @type prometheus
+    @id in_prometheus6
+    bind "::"
+    port {{ .Monitor.Port }}
+{{- if .Monitor.Path }}
+    metrics_path {{ .Monitor.Path }}
+{{- end }}
+</source>
 <source>
     @type prometheus_monitor
 </source>