[master] do sync grow request only if absolutely necessary (#5821)

* do sync grow request only if absolutely necessary
https://github.com/seaweedfs/seaweedfs/pull/5819

* remove check VolumeGrowStrategy Threshold on PickForWrite

* fix fmt.Errorf

weed/stats/metrics.go

@@ -78,6 +78,14 @@ var (
 			Help:      "Number of volumes in volume layouts",
 		}, []string{"collection", "dataCenter", "type"})
 
+	MasterPickForWriteErrorCounter = prometheus.NewCounter(
+		prometheus.CounterOpts{
+			Namespace: Namespace,
+			Subsystem: "master",
+			Name:      "pick_for_write_error",
+			Help:      "Counter of master pick for write error",
+		})
+
 	MasterLeaderChangeCounter = prometheus.NewCounterVec(
 		prometheus.CounterOpts{
 			Namespace: Namespace,