[s3] fix s3 test_multipart_resend_first_finishes_last (#5471)

* try fix s3 test
https://github.com/seaweedfs/seaweedfs/pull/5466

* add error handler metrics

* refactor

* refactor multipartExt

* delete bad entry parts

weed/stats/metrics.go

@@ -241,7 +241,13 @@ var (
 			Name:      "request_total",
 			Help:      "Counter of s3 requests.",
 		}, []string{"type", "code", "bucket"})
-
+	S3HandlerCounter = prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Namespace: Namespace,
+			Subsystem: "s3",
+			Name:      "handler_total",
+			Help:      "Counter of s3 server handlers.",
+		}, []string{"type"})
 	S3RequestHistogram = prometheus.NewHistogramVec(
 		prometheus.HistogramOpts{
 			Namespace: Namespace,
@@ -292,6 +298,7 @@ func init() {
 	Gather.MustRegister(VolumeServerResourceGauge)
 
 	Gather.MustRegister(S3RequestCounter)
+	Gather.MustRegister(S3HandlerCounter)
 	Gather.MustRegister(S3RequestHistogram)
 	Gather.MustRegister(S3TimeToFirstByteHistogram)
 }