Use create_volume wrapper for volume creation

Since we use this method the resource_cleanup isn't necessary any more,
besides admin privileges isn't required for volume creation.

Change-Id: Ia0d8406525b2a81a9e2b750dfbc433b61d289985
diff --git a/tempest/api/volume/admin/test_multi_backend.py b/tempest/api/volume/admin/test_multi_backend.py
index 2db8010..c0891e4 100644
--- a/tempest/api/volume/admin/test_multi_backend.py
+++ b/tempest/api/volume/admin/test_multi_backend.py
@@ -66,8 +66,7 @@
 
         params = {'name': vol_name, 'volume_type': type_name,
                   'size': CONF.volume.volume_size}
-        cls.volume = cls.admin_volume_client.create_volume(
-            **params)['volume']
+        cls.volume = cls.create_volume(**params)
         if with_prefix:
             cls.volume_id_list_with_prefix.append(cls.volume['id'])
         else:
@@ -76,21 +75,6 @@
         waiters.wait_for_volume_resource_status(cls.admin_volume_client,
                                                 cls.volume['id'], 'available')
 
-    @classmethod
-    def resource_cleanup(cls):
-        # volumes deletion
-        vid_prefix = getattr(cls, 'volume_id_list_with_prefix', [])
-        for volume_id in vid_prefix:
-            cls.admin_volume_client.delete_volume(volume_id)
-            cls.admin_volume_client.wait_for_resource_deletion(volume_id)
-
-        vid_no_pre = getattr(cls, 'volume_id_list_without_prefix', [])
-        for volume_id in vid_no_pre:
-            cls.admin_volume_client.delete_volume(volume_id)
-            cls.admin_volume_client.wait_for_resource_deletion(volume_id)
-
-        super(VolumeMultiBackendTest, cls).resource_cleanup()
-
     @decorators.idempotent_id('c1a41f3f-9dad-493e-9f09-3ff197d477cc')
     def test_backend_name_reporting(self):
         # get volume id which created by type without prefix