Fix finding router for scenario tests

Finding router return tuple resp,body and body only contains router details.
Closes-Bug: 1375859
Change-Id: Ic405d20991561e8773153d829750826a82ed751c
diff --git a/tempest/scenario/manager.py b/tempest/scenario/manager.py
index 9933646..5c18ddf 100644
--- a/tempest/scenario/manager.py
+++ b/tempest/scenario/manager.py
@@ -934,8 +934,8 @@
         router_id = CONF.network.public_router_id
         network_id = CONF.network.public_network_id
         if router_id:
-            result = client.show_router(router_id)
-            return net_resources.AttributeDict(**result['router'])
+            resp, body = client.show_router(router_id)
+            return net_resources.AttributeDict(**body['router'])
         elif network_id:
             router = self._create_router(client, tenant_id)
             router.set_gateway(network_id)