Fix duplicate collectors

pkg/bench/get.go

@@ -113,7 +113,7 @@ func (g *Get) Prepare(ctx context.Context) error {
 			return (fmt.Errorf("no objects found for bucket %s", g.Bucket))
 		}
 		done()
-		g.Collector = NewCollector()
+		g.addCollector()
 		return nil
 	}
 
@@ -141,7 +141,6 @@ func (g *Get) Prepare(ctx context.Context) error {
 
 	var wg sync.WaitGroup
 	wg.Add(g.Concurrency)
-	g.addCollector()
 
 	obj := make(chan struct{}, g.CreateObjects)
 	for i := 0; i < g.CreateObjects; i++ {

pkg/bench/list.go

@@ -34,8 +34,7 @@ import (
 // List benchmarks listing speed.
 type List struct {
 	Common
-	Collector *Collector
-	objects   []generator.Objects
+	objects []generator.Objects
 
 	CreateObjects int
 	Versions      int

pkg/bench/mixed.go

@@ -35,8 +35,7 @@ import (
 // Mixed benchmarks mixed operations all inclusive.
 type Mixed struct {
 	Common
-	Collector *Collector
-	Dist      *MixedDistribution
+	Dist *MixedDistribution
 
 	GetOpts       minio.GetObjectOptions
 	StatOpts      minio.StatObjectOptions

pkg/bench/select.go

@@ -34,7 +34,6 @@ import (
 // Select benchmarks download speed.
 type Select struct {
 	Common
-	Collector *Collector
 
 	// Default Select options.
 	SelectOpts minio.SelectObjectOptions