Adds ability to define a prefix for etcd paths

The API server can be supplied (via a command line flag) with a custom
prefix that is prepended to etcd resources paths.

Refs: #3476

test/integration/etcd_tools_test.go

@@ -26,6 +26,7 @@ import (
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/api/testapi"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/runtime"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/tools"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/tools/etcdtest"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/watch"
 )
 
@@ -92,8 +93,9 @@ func TestExtractObj(t *testing.T) {
 
 func TestWatch(t *testing.T) {
 	client := newEtcdClient()
-	helper := tools.NewEtcdHelper(client, testapi.Codec())
+	helper := tools.NewEtcdHelper(client, testapi.Codec(), etcdtest.PathPrefix())
 	withEtcdKey(func(key string) {
+		key = etcdtest.AddPrefix(key)
 		resp, err := client.Set(key, runtime.EncodeOrDie(testapi.Codec(), &api.Pod{ObjectMeta: api.ObjectMeta{Name: "foo"}}), 0)
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)