Fix lint issues reported by staticcheck

Used staticcheck 2022.1.2 (v0.3.2)

See: staticcheck.io

fs/accounting/accounting.go

@@ -444,7 +444,7 @@ func (acc *Account) speed() (bps, current float64) {
 		return 0, 0
 	}
 	// Calculate speed from first read.
-	total := float64(time.Now().Sub(acc.values.start)) / float64(time.Second)
+	total := float64(time.Since(acc.values.start)) / float64(time.Second)
 	if total > 0 {
 		bps = float64(acc.values.bytes) / total
 	} else {

fs/accounting/stats_groups_test.go

@@ -111,9 +111,9 @@ func TestStatsGroupOperations(t *testing.T) {
 		runtime.GC()
 		runtime.ReadMemStats(&end)
 
-		t.Log(fmt.Sprintf("%+v\n%+v", start, end))
+		t.Logf("%+v\n%+v", start, end)
 		diff := percentDiff(start.HeapObjects, end.HeapObjects)
-		if diff > 1 || diff < 0 {
+		if diff > 1 {
 			t.Errorf("HeapObjects = %d, expected %d", end.HeapObjects, start.HeapObjects)
 		}
 	})