Replace "hardcode" in scenario tests

Replace "harcode" of device name for attached volume, like "vdb",
by option CONF.compute.volume_device_name in all scenario tests.

Change-Id: I1d390d95345367a8a29ac990429619fa044563a3
Closes-Bug: 1458649
diff --git a/tempest/scenario/manager.py b/tempest/scenario/manager.py
index 50aa261..849da01 100644
--- a/tempest/scenario/manager.py
+++ b/tempest/scenario/manager.py
@@ -407,9 +407,9 @@
         return snapshot_image
 
     def nova_volume_attach(self):
-        # TODO(andreaf) Device should be here CONF.compute.volume_device_name
         volume = self.servers_client.attach_volume(
-            self.server['id'], self.volume['id'], '/dev/vdb')
+            self.server['id'], self.volume['id'], '/dev/%s'
+            % CONF.compute.volume_device_name)
         self.assertEqual(self.volume['id'], volume['id'])
         self.volumes_client.wait_for_volume_status(volume['id'], 'in-use')
         # Refresh the volume after the attachment