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/secret_test.go

@@ -30,6 +30,7 @@ import (
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/apiserver"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/client"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/master"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/tools/etcdtest"
 	"github.com/GoogleCloudPlatform/kubernetes/plugin/pkg/admission/admit"
 )
 
@@ -50,7 +51,7 @@ func deleteSecretOrErrorf(t *testing.T, c *client.Client, ns, name string) {
 
 // TestSecrets tests apiserver-side behavior of creation of secret objects and their use by pods.
 func TestSecrets(t *testing.T) {
-	helper, err := master.NewEtcdHelper(newEtcdClient(), testapi.Version())
+	helper, err := master.NewEtcdHelper(newEtcdClient(), testapi.Version(), etcdtest.PathPrefix())
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}