Use classname as prefix of volume name

Sometimes volume may not be cleaned properly and from its name
(such as tempest-Volume-245831117) it is difficult to know which
testcase created it. This is to use classname as prefix of volume
name.

Change-Id: Ic0e376098caa0c46473d92f6d043ab85fbbaee8c
diff --git a/tempest/api/volume/admin/test_multi_backend.py b/tempest/api/volume/admin/test_multi_backend.py
index b7c4236..f665e69 100644
--- a/tempest/api/volume/admin/test_multi_backend.py
+++ b/tempest/api/volume/admin/test_multi_backend.py
@@ -55,8 +55,8 @@
     @classmethod
     def _create_type_and_volume(cls, backend_name_key, with_prefix):
         # Volume/Type creation
-        type_name = data_utils.rand_name('Type')
-        vol_name = data_utils.rand_name('Volume')
+        type_name = data_utils.rand_name(cls.__name__ + '-Type')
+        vol_name = data_utils.rand_name(cls.__name__ + '-Volume')
         spec_key_with_prefix = "capabilities:volume_backend_name"
         spec_key_without_prefix = "volume_backend_name"
         if with_prefix: