Fix param storage_protocol

Change-Id: Idfe9be05a4ebd677f7162e1a8bbd1ce96cc3927a
diff --git a/_modules/runtest/tempest_sections/volume.py b/_modules/runtest/tempest_sections/volume.py
index df24023..7deeeb1 100644
--- a/_modules/runtest/tempest_sections/volume.py
+++ b/_modules/runtest/tempest_sections/volume.py
@@ -74,7 +74,7 @@
     def storage_protocol(self):
         c = conditions.BaseRule('cinder.volume.enabled', 'eq', True)
         backends = self.get_item_when_condition_match(
-            'cinder.controller.backend', c)
+            'cinder.volume.backend', c)
         if not backends:
             return