Add existing volumes when using pre-provisioned credentials

When using pre-provisioned credentials, the tenant may have
volumes other than those created in the testcase and so will
make test_volume_list_param_tenant fail unexpectedly. e.g. the
existing volumes may be those not being deleted successfully
and ending up with status 'ERROR', which is not rare seen in
production clouds. So this is to add existing volumes in
test_volume_list_param_tenant.

Change-Id: Ice975b2011e7914d2b92ea71e5dd30f9074f6243
Closes-Bug: #1618730
diff --git a/tempest/api/volume/admin/v2/test_volumes_list.py b/tempest/api/volume/admin/v2/test_volumes_list.py
index 4437803..cdd9df9 100644
--- a/tempest/api/volume/admin/v2/test_volumes_list.py
+++ b/tempest/api/volume/admin/v2/test_volumes_list.py
@@ -29,7 +29,9 @@
     def resource_setup(cls):
         super(VolumesListAdminV2TestJSON, cls).resource_setup()
         # Create 3 test volumes
-        cls.volume_list = []
+        # NOTE(zhufl): When using pre-provisioned credentials, the project
+        # may have volumes other than those created below.
+        cls.volume_list = cls.volumes_client.list_volumes()['volumes']
         for i in range(3):
             volume = cls.create_volume()
             # Fetch volume details
@@ -59,5 +61,6 @@
         # primary tenant
         fetched_tenant_id = [operator.itemgetter(
             'os-vol-tenant-attr:tenant_id')(item) for item in fetched_list]
-        expected_tenant_id = [self.volumes_client.tenant_id] * 3
+        expected_tenant_id = [self.volumes_client.tenant_id] * \
+            len(self.volume_list)
         self.assertEqual(expected_tenant_id, fetched_tenant_id)