Added +inf bucket for quantile computations

Author: ahg-g

staging/src/k8s.io/component-base/metrics/testutil/metrics.go

@@ -286,8 +286,14 @@ func (hist *Histogram) Quantile(q float64) float64 {
 		})
 	}
 
-	// bucketQuantile expects the upper bound of the last bucket to be +inf
-	// buckets[len(buckets)-1].upperBound = math.Inf(+1)
+	if len(buckets) == 0 || buckets[len(buckets)-1].upperBound != math.Inf(+1) {
+		// The list of buckets in dto.Histogram doesn't include the final +Inf bucket, so we
+		// add it here for the reset of the samples.
+		buckets = append(buckets, bucket{
+			count:      float64(hist.GetSampleCount()),
+			upperBound: math.Inf(+1),
+		})
+	}
 
 	return bucketQuantile(q, buckets)
 }