Update volume client class description

It is not more a base class for volume clients,
only for volume client v1.

Change-Id: Id7e8f24da50a1e5d0305932e35939cb428f0e683
diff --git a/tempest/lib/services/volume/v1/volumes_client.py b/tempest/lib/services/volume/v1/volumes_client.py
index 3df8da4..cc98c91 100644
--- a/tempest/lib/services/volume/v1/volumes_client.py
+++ b/tempest/lib/services/volume/v1/volumes_client.py
@@ -22,7 +22,7 @@
 
 
 class VolumesClient(rest_client.RestClient):
-    """Base client class to send CRUD Volume API requests"""
+    """Client class to send CRUD Volume V1 API requests"""
 
     def _prepare_params(self, params):
         """Prepares params for use in get or _ext_get methods.