unit tests for the volume plugin name that's used inside GeneratedUnmapVolumeFunc for csi migration on/off scenarios

Signed-off-by: Mucahit Kurt <mucahitkurt@gmail.com>

pkg/controller/.import-restrictions

@@ -104,6 +104,7 @@
         "github.com/robfig/cron",
         "github.com/spf13/pflag",
         "github.com/stretchr/testify/assert",
+        "github.com/stretchr/testify/mock",
         "github.com/stretchr/testify/require",
         "github.com/google/gofuzz",
         "github.com/golang/protobuf/ptypes/wrappers",
@@ -162,6 +163,7 @@
         "k8s.io/client-go/util/flowcontrol",
         "k8s.io/client-go/util/retry",
         "k8s.io/client-go/util/workqueue",
+        "k8s.io/client-go/util/testing",
 	"k8s.io/client-go/transport"
       ]
     },