Default to noop metric provider

With the built in prom. metrics provider, the k8s machinery doesnt
deregister metrics when controllers are removed. So over time as
things like clusters are created or removed the metrics are not
cleaned up. The metrics types for the cache and queue are also
very large. They can take ~1GB of RAM in a 100 cluster setup.

Also, Rancher is not exposing these stats so they are unobservable.

controller/generic_controller.go

@@ -3,6 +3,7 @@ package controller
 import (
 	"context"
 	"fmt"
+	"os"
 	"strings"
 	"sync"
 	"time"
@@ -22,10 +23,19 @@ import (
 	"k8s.io/client-go/util/workqueue"
 )
 
+const MetricsEnv = "NORMAN_QUEUE_METRICS"
+
 var (
 	resyncPeriod = 2 * time.Hour
 )
 
+// Override the metrics providers
+func init() {
+	if os.Getenv(MetricsEnv) != "true" {
+		DisableAllControllerMetrics()
+	}
+}
+
 type HandlerFunc func(key string) error
 
 type GenericController interface {