Refactor volume clone tests

Creating a common method 'volume_clone_verification' in order to
reduce a duplicated code.

Change-Id: If73ab72d0ce3218a6a3ba8b5a5c812507d800a21
diff --git a/tempest/api/volume/test_volumes_clone.py b/tempest/api/volume/test_volumes_clone.py
index 4c13375..927bfa5 100644
--- a/tempest/api/volume/test_volumes_clone.py
+++ b/tempest/api/volume/test_volumes_clone.py
@@ -30,6 +30,18 @@
         if not CONF.volume_feature_enabled.clone:
             raise cls.skipException("Cinder volume clones are disabled")
 
+    def _verify_volume_clone(self, source_volume, cloned_volume,
+                             bootable='false', extra_size=0):
+
+        cloned_vol_details = self.volumes_client.show_volume(
+            cloned_volume['id'])['volume']
+
+        self.assertEqual(source_volume['id'],
+                         cloned_vol_details['source_volid'])
+        self.assertEqual(source_volume['size'] + extra_size,
+                         cloned_vol_details['size'])
+        self.assertEqual(bootable, cloned_vol_details['bootable'])
+
     @decorators.idempotent_id('9adae371-a257-43a5-9555-dc7c88e66e0e')
     def test_create_from_volume(self):
         # Creates a volume from another volume passing a size different from
@@ -41,10 +53,7 @@
         dst_vol = self.create_volume(source_volid=src_vol['id'],
                                      size=src_size + 1)
 
-        volume = self.volumes_client.show_volume(dst_vol['id'])['volume']
-        # Should allow
-        self.assertEqual(volume['source_volid'], src_vol['id'])
-        self.assertEqual(volume['size'], src_size + 1)
+        self._verify_volume_clone(src_vol, dst_vol, extra_size=1)
 
     @decorators.idempotent_id('cbbcd7c6-5a6c-481a-97ac-ca55ab715d16')
     @test.services('image')
@@ -55,10 +64,5 @@
 
         # Create a volume from the bootable volume
         cloned_vol = self.create_volume(source_volid=src_vol['id'])
-        cloned_vol_details = self.volumes_client.show_volume(
-            cloned_vol['id'])['volume']
 
-        # Verify cloned volume creation as expected
-        self.assertEqual('true', cloned_vol_details['bootable'])
-        self.assertEqual(src_vol['id'], cloned_vol_details['source_volid'])
-        self.assertEqual(src_vol['size'], cloned_vol_details['size'])
+        self._verify_volume_clone(src_vol, cloned_vol, bootable='true')