Roll back pkg client code for Velero server

Signed-off-by: danfengl <danfengl@vmware.com>

test/e2e/pkg/client/client.go

@@ -0,0 +1,70 @@
+/*
+Copyright 2017, 2019 the Velero contributors.
+
+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 client
+
+import (
+	"fmt"
+	"runtime"
+
+	"github.com/pkg/errors"
+	"k8s.io/client-go/rest"
+	"k8s.io/client-go/tools/clientcmd"
+
+	"github.com/vmware-tanzu/velero/pkg/buildinfo"
+)
+
+func buildConfigFromFlags(context, kubeconfigPath string, precedence []string) (*rest.Config, error) {
+	return clientcmd.NewNonInteractiveDeferredLoadingClientConfig(
+		&clientcmd.ClientConfigLoadingRules{ExplicitPath: kubeconfigPath, Precedence: precedence},
+		&clientcmd.ConfigOverrides{
+			CurrentContext: context,
+		}).ClientConfig()
+}
+
+// Config returns a *rest.Config, using either the kubeconfig (if specified) or an in-cluster
+// configuration.
+func Config(kubeconfig, kubecontext, baseName string, qps float32, burst int) (*rest.Config, error) {
+	loadingRules := clientcmd.NewDefaultClientConfigLoadingRules()
+	loadingRules.ExplicitPath = kubeconfig
+	clientConfig, err := buildConfigFromFlags(kubecontext, kubeconfig, loadingRules.Precedence)
+	if err != nil {
+		return nil, errors.Wrap(err, "error finding Kubernetes API server config in --kubeconfig, $KUBECONFIG, or in-cluster configuration")
+	}
+
+	if qps > 0.0 {
+		clientConfig.QPS = qps
+	}
+	if burst > 0 {
+		clientConfig.Burst = burst
+	}
+
+	clientConfig.UserAgent = buildUserAgent(
+		baseName,
+		buildinfo.Version,
+		buildinfo.FormattedGitSHA(),
+		runtime.GOOS,
+		runtime.GOARCH,
+	)
+
+	return clientConfig, nil
+}
+
+// buildUserAgent builds a User-Agent string from given args.
+func buildUserAgent(command, version, formattedSha, os, arch string) string {
+	return fmt.Sprintf(
+		"%s/%s (%s/%s) %s", command, version, os, arch, formattedSha)
+}