allow sha256 payload to be configurable for object perf test (#18712)

Signed-off-by: Zhou Ting <ting.z.zhou@intel.com>

cmd/admin-handlers.go

@@ -1297,6 +1297,7 @@ func (a adminAPIHandlers) ObjectSpeedTestHandler(w http.ResponseWriter, r *http.
 	customBucket := strings.TrimSpace(r.Form.Get(peerRESTBucket))
 	autotune := r.Form.Get("autotune") == "true"
 	noClear := r.Form.Get("noclear") == "true"
+	enableSha256 := r.Form.Get("enableSha256") == "true"
 
 	size, err := strconv.Atoi(sizeStr)
 	if err != nil {
@@ -1366,6 +1367,7 @@ func (a adminAPIHandlers) ObjectSpeedTestHandler(w http.ResponseWriter, r *http.
 		autotune:         autotune,
 		storageClass:     storageClass,
 		bucketName:       customBucket,
+		enableSha256:     enableSha256,
 	})
 	var prevResult madmin.SpeedTestResult
 	for {