Upgrade k8s.io/client-go to kubernetes-1.9.1

Upgraded from 99c19923, branch release-3.0.

This required fetching or upgrading the following:
* k8s.io/api to kubernetes-1.9.1
* k8s.io/apimachinery to kubernetes-1.9.1
* github.com/juju/ratelimit to 1.0.1
* github.com/spf13/pflag to 4c012f6d

Also, update Scope's imports/function calls to be compatible with the new client.

vendor/github.com/gophercloud/gophercloud/internal/pkg.go

@@ -0,0 +1 @@
+package internal

vendor/github.com/gophercloud/gophercloud/internal/testing/pkg.go

@@ -0,0 +1 @@
+package testing

vendor/github.com/gophercloud/gophercloud/internal/util.go

@@ -0,0 +1,34 @@
+package internal
+
+import (
+	"reflect"
+	"strings"
+)
+
+// RemainingKeys will inspect a struct and compare it to a map. Any struct
+// field that does not have a JSON tag that matches a key in the map or
+// a matching lower-case field in the map will be returned as an extra.
+//
+// This is useful for determining the extra fields returned in response bodies
+// for resources that can contain an arbitrary or dynamic number of fields.
+func RemainingKeys(s interface{}, m map[string]interface{}) (extras map[string]interface{}) {
+	extras = make(map[string]interface{})
+	for k, v := range m {
+		extras[k] = v
+	}
+
+	valueOf := reflect.ValueOf(s)
+	typeOf := reflect.TypeOf(s)
+	for i := 0; i < valueOf.NumField(); i++ {
+		field := typeOf.Field(i)
+
+		lowerField := strings.ToLower(field.Name)
+		delete(extras, lowerField)
+
+		if tagValue := field.Tag.Get("json"); tagValue != "" && tagValue != "-" {
+			delete(extras, tagValue)
+		}
+	}
+
+	return
+}