Disable Intree GCE PD tests by default

Signed-off-by: Davanum Srinivas <davanum@gmail.com>

test/e2e/storage/in_tree_volumes.go

@@ -17,6 +17,8 @@ limitations under the License.
 package storage
 
 import (
+	"os"
+
 	"github.com/onsi/ginkgo"
 	"k8s.io/kubernetes/test/e2e/storage/drivers"
 	storageframework "k8s.io/kubernetes/test/e2e/storage/framework"
@@ -35,8 +37,6 @@ var testDrivers = []func() storageframework.TestDriver{
 	drivers.InitHostPathSymlinkDriver,
 	drivers.InitEmptydirDriver,
 	drivers.InitCinderDriver,
-	drivers.InitGcePdDriver,
-	drivers.InitWindowsGcePdDriver,
 	drivers.InitVSphereDriver,
 	drivers.InitAzureDiskDriver,
 	drivers.InitAzureFileDriver,
@@ -53,6 +53,10 @@ var testDrivers = []func() storageframework.TestDriver{
 
 // This executes testSuites for in-tree volumes.
 var _ = utils.SIGDescribe("In-tree Volumes", func() {
+	if enableGcePD := os.Getenv("ENABLE_STORAGE_GCE_PD_DRIVER"); enableGcePD == "yes" {
+		testDrivers = append(testDrivers, drivers.InitGcePdDriver)
+		testDrivers = append(testDrivers, drivers.InitWindowsGcePdDriver)
+	}
 	for _, initDriver := range testDrivers {
 		curDriver := initDriver()