e2e/storage: ensure that also external storage classes are unique

One previously undocumented expectation is that
GetDynamicProvisionStorageClass can be called more than once per test
and then each time returns a new, unique storage class. The in-memory
implementation in driveroperations.go:GetStorageClass ensured that,
but loading from a .yaml file didn't. This caused the multivolume tests
to fail when applied to an already installed GCE driver with the
-storage.testdriver parameter.

test/e2e/storage/external/BUILD

@@ -11,6 +11,7 @@ go_library(
         "//staging/src/k8s.io/apimachinery/pkg/runtime:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/runtime/schema:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/util/sets:go_default_library",
+        "//staging/src/k8s.io/apiserver/pkg/storage/names:go_default_library",
         "//staging/src/k8s.io/client-go/kubernetes/scheme:go_default_library",
         "//test/e2e/framework:go_default_library",
         "//test/e2e/storage/testpatterns:go_default_library",

test/e2e/storage/external/external.go

@@ -27,6 +27,7 @@ import (
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/apimachinery/pkg/util/sets"
+	"k8s.io/apiserver/pkg/storage/names"
 	"k8s.io/client-go/kubernetes/scheme"
 	"k8s.io/kubernetes/test/e2e/framework"
 	"k8s.io/kubernetes/test/e2e/storage/testpatterns"
@@ -242,6 +243,9 @@ func (d *driverDefinition) GetDynamicProvisionStorageClass(config *testsuites.Pe
 
 	sc, ok := items[0].(*storagev1.StorageClass)
 	gomega.Expect(ok).To(gomega.BeTrue(), "storage class from %s", d.StorageClass.FromFile)
+	// Ensure that we can load more than once as required for
+	// GetDynamicProvisionStorageClass by adding a random suffix.
+	sc.Name = names.SimpleNameGenerator.GenerateName(sc.Name + "-")
 	if fsType != "" {
 		if sc.Parameters == nil {
 			sc.Parameters = map[string]string{}

test/e2e/storage/testsuites/testdriver.go

@@ -88,6 +88,9 @@ type PreprovisionedPVTestDriver interface {
 type DynamicPVTestDriver interface {
 	TestDriver
 	// GetDynamicProvisionStorageClass returns a StorageClass dynamic provision Persistent Volume.
+	// The StorageClass must be created in the current test's namespace and have
+	// a unique name inside that namespace because GetDynamicProvisionStorageClass might
+	// be called more than once per test.
 	// It will set fsType to the StorageClass, if TestDriver supports it.
 	// It will return nil, if the TestDriver doesn't support it.
 	GetDynamicProvisionStorageClass(config *PerTestConfig, fsType string) *storagev1.StorageClass