cinder v2 api tests - fix volume client

This is a legacy problem in change
I712a90d39981564af09393ed1b7f4be12897c808

1. move cls.volumes_client, cls.volumes_extension_client
   cls.snapshots_client from BaseVolumeTest into
   subclass(BaseVolumeV1Test)
2. delete call cls.volumes_client.keystone_auth as it is
   called automatically in request method of RestClient.

Change-Id: I5184de9911e3fe9a3c23c2c4f84e59596f10b77c
Implements: blueprint cinder-v2-api-tests
diff --git a/tempest/api/volume/base.py b/tempest/api/volume/base.py
index 9c841cc..4c6b430 100644
--- a/tempest/api/volume/base.py
+++ b/tempest/api/volume/base.py
@@ -37,10 +37,7 @@
 
         cls.os = cls.get_client_manager()
 
-        cls.volumes_client = cls.os.volumes_client
-        cls.snapshots_client = cls.os.snapshots_client
         cls.servers_client = cls.os.servers_client
-        cls.volumes_extension_client = cls.os.volumes_extension_client
         cls.image_ref = cls.config.compute.image_ref
         cls.flavor_ref = cls.config.compute.flavor_ref
         cls.build_interval = cls.config.volume.build_interval
@@ -117,12 +114,9 @@
             msg = "Volume API v1 not supported"
             raise cls.skipException(msg)
         super(BaseVolumeV1Test, cls).setUpClass()
+        cls.snapshots_client = cls.os.snapshots_client
         cls.volumes_client = cls.os.volumes_client
-        cls.volumes_client.keystone_auth(cls.os.username,
-                                         cls.os.password,
-                                         cls.os.auth_url,
-                                         cls.volumes_client.service,
-                                         cls.os.tenant_name)
+        cls.volumes_extension_client = cls.os.volumes_extension_client
 
 
 class BaseVolumeV1AdminTest(BaseVolumeV1Test):
diff --git a/tempest/api/volume/test_extensions.py b/tempest/api/volume/test_extensions.py
index 546c430..4c012e2 100644
--- a/tempest/api/volume/test_extensions.py
+++ b/tempest/api/volume/test_extensions.py
@@ -24,7 +24,7 @@
 LOG = logging.getLogger(__name__)
 
 
-class ExtensionsTestJSON(base.BaseVolumeTest):
+class ExtensionsTestJSON(base.BaseVolumeV1Test):
     _interface = 'json'
 
     @attr(type='gate')
diff --git a/tempest/api/volume/test_volume_metadata.py b/tempest/api/volume/test_volume_metadata.py
index 0909ade..3152a4c 100644
--- a/tempest/api/volume/test_volume_metadata.py
+++ b/tempest/api/volume/test_volume_metadata.py
@@ -15,11 +15,11 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-from tempest.api.volume.base import BaseVolumeTest
+from tempest.api.volume import base
 from tempest import test
 
 
-class VolumeMetadataTest(BaseVolumeTest):
+class VolumeMetadataTest(base.BaseVolumeV1Test):
     _interface = "json"
 
     @classmethod