Remove CONF values from volume clients

To move volume clients to tempest-lib, this patch moves
CONF values from volume clients to the client setting.

Change-Id: Iddd8306723c1ff33105f513c1993a0497a949c29
Depends-on: Ic86739dde83dcac8f68e53599967de53694f692f
diff --git a/tempest/services/volume/json/volumes_client.py b/tempest/services/volume/json/volumes_client.py
index c0f81fe..d834905 100644
--- a/tempest/services/volume/json/volumes_client.py
+++ b/tempest/services/volume/json/volumes_client.py
@@ -20,12 +20,11 @@
 from tempest.common import service_client
 from tempest import config
 from tempest import exceptions
-from tempest.services.volume.json import base
 
 CONF = config.CONF
 
 
-class BaseVolumesClientJSON(base.VolumeClient):
+class BaseVolumesClientJSON(service_client.ServiceClient):
     """
     Base client class to send CRUD Volume API requests to a Cinder endpoint
     """