Fix client usage in multibackend volume test

This commit fixes the client usage in the multibackend volume api
tests. There was no reason for the test to initialize new instances
of the clients directly. Firstly this wasn't tenant isolation safe
and secondly the clients are already instantiated with admin credentials
in the base admin class setUpClass(). This commit just switches the
tests to use those clients instead.

Change-Id: Ifc986b82dcfe872ff1b25babd78ab90e996d5c12
diff --git a/tempest/api/volume/admin/test_multi_backend.py b/tempest/api/volume/admin/test_multi_backend.py
index cb1a6cb..b0c878b 100644
--- a/tempest/api/volume/admin/test_multi_backend.py
+++ b/tempest/api/volume/admin/test_multi_backend.py
@@ -14,8 +14,6 @@
 from tempest.common.utils import data_utils
 from tempest import config
 from tempest.openstack.common import log as logging
-from tempest.services.volume.json.admin import volume_types_client
-from tempest.services.volume.json import volumes_client
 from tempest.test import attr
 
 CONF = config.CONF
@@ -36,20 +34,7 @@
         cls.backend1_name = CONF.volume.backend1_name
         cls.backend2_name = CONF.volume.backend2_name
 
-        adm_user = CONF.identity.admin_username
-        adm_pass = CONF.identity.admin_password
-        adm_tenant = CONF.identity.admin_tenant_name
-        auth_url = CONF.identity.uri
-
-        cls.volume_client = volumes_client.VolumesClientJSON(adm_user,
-                                                             adm_pass,
-                                                             auth_url,
-                                                             adm_tenant)
-        cls.type_client = volume_types_client.VolumeTypesClientJSON(adm_user,
-                                                                    adm_pass,
-                                                                    auth_url,
-                                                                    adm_tenant)
-
+        cls.volume_client = cls.os_adm.volumes_client
         cls.volume_type_id_list = []
         cls.volume_id_list = []
         try:
@@ -57,7 +42,7 @@
             type1_name = data_utils.rand_name('Type-')
             vol1_name = data_utils.rand_name('Volume-')
             extra_specs1 = {"volume_backend_name": cls.backend1_name}
-            resp, cls.type1 = cls.type_client.create_volume_type(
+            resp, cls.type1 = cls.client.create_volume_type(
                 type1_name, extra_specs=extra_specs1)
             cls.volume_type_id_list.append(cls.type1['id'])
 
@@ -72,7 +57,7 @@
                 type2_name = data_utils.rand_name('Type-')
                 vol2_name = data_utils.rand_name('Volume-')
                 extra_specs2 = {"volume_backend_name": cls.backend2_name}
-                resp, cls.type2 = cls.type_client.create_volume_type(
+                resp, cls.type2 = cls.client.create_volume_type(
                     type2_name, extra_specs=extra_specs2)
                 cls.volume_type_id_list.append(cls.type2['id'])
 
@@ -97,7 +82,7 @@
         # volume types deletion
         volume_type_id_list = getattr(cls, 'volume_type_id_list', [])
         for volume_type_id in volume_type_id_list:
-            cls.type_client.delete_volume_type(volume_type_id)
+            cls.client.delete_volume_type(volume_type_id)
 
         super(VolumeMultiBackendTest, cls).tearDownClass()