update dependencies

Ran a `go get -u` and bumped K8s deps to 1.15.0.

Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

vendor/github.com/docker/go-metrics/helpers.go

@@ -0,0 +1,10 @@
+package metrics
+
+func sumFloat64(vs ...float64) float64 {
+	var sum float64
+	for _, v := range vs {
+		sum += v
+	}
+
+	return sum
+}