Granular control for metric collection

We see an issue where a BMC is reporting 42+ ethernet
interfaces and not returning any data for them. This is likely
a bug in the BMC FW.

This patch allows skipping the collection of certain groups
of metrics to work around the bug. It adds an optional
configuration section which can be used to control what is
collected.

Author: dougszumski

collector/redfish_collector.go

@@ -40,15 +40,15 @@ type RedfishCollector struct {
 }
 
 // NewRedfishCollector return RedfishCollector
-func NewRedfishCollector(host string, username string, password string, collectLogs bool, logger *log.Entry) *RedfishCollector {
+func NewRedfishCollector(host string, username string, password string, collectLogs bool, disabledMetrics []string, logger *log.Entry) *RedfishCollector {
 	var collectors map[string]prometheus.Collector
 	collectorLogCtx := logger
 	redfishClient, err := newRedfishClient(host, username, password)
 	if err != nil {
 		collectorLogCtx.WithError(err).Error("error creating redfish client")
 	} else {
 		chassisCollector := NewChassisCollector(redfishClient, collectLogs, collectorLogCtx)
-		systemCollector := NewSystemCollector(redfishClient, collectLogs, collectorLogCtx)
+		systemCollector := NewSystemCollector(redfishClient, collectLogs, disabledMetrics, collectorLogCtx)
 		managerCollector := NewManagerCollector(redfishClient, collectLogs, collectorLogCtx)
 
 		collectors = map[string]prometheus.Collector{"chassis": chassisCollector, "system": systemCollector, "manager": managerCollector}