Refactor kubelet server into its own package

Refactor Kubelet's server functionality into a server package. Most
notably, move pkg/kubelet/server.go into
pkg/kubelet/server/server.go. This will lead to better separation of
concerns and a more readable code hierarchy.

pkg/kubelet/server/auth.go

@@ -0,0 +1,37 @@
+/*
+Copyright 2015 The Kubernetes Authors All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package server
+
+import (
+	"k8s.io/kubernetes/pkg/auth/authenticator"
+	"k8s.io/kubernetes/pkg/auth/authorizer"
+)
+
+// KubeletAuth implements AuthInterface
+type KubeletAuth struct {
+	// authenticator identifies the user for requests to the Kubelet API
+	authenticator.Request
+	// authorizerAttributeGetter builds authorization.Attributes for a request to the Kubelet API
+	authorizer.RequestAttributesGetter
+	// authorizer determines whether a given authorization.Attributes is allowed
+	authorizer.Authorizer
+}
+
+// NewKubeletAuth returns a kubelet.AuthInterface composed of the given authenticator, attribute getter, and authorizer
+func NewKubeletAuth(authenticator authenticator.Request, authorizerAttributeGetter authorizer.RequestAttributesGetter, authorizer authorizer.Authorizer) AuthInterface {
+	return &KubeletAuth{authenticator, authorizerAttributeGetter, authorizer}
+}