Update vendor

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

@@ -0,0 +1,15 @@
+package metrics
+
+import "github.com/prometheus/client_golang/prometheus"
+
+// Register adds all the metrics in the provided namespace to the global
+// metrics registry
+func Register(n *Namespace) {
+	prometheus.MustRegister(n)
+}
+
+// Deregister removes all the metrics in the provided namespace from the
+// global metrics registry
+func Deregister(n *Namespace) {
+	prometheus.Unregister(n)
+}