Adapt to the recent tempest

Update after the recently merged tempest change. [1]

[1] I50759d32e47d975ec64ca129a13b2ae4459917e4

Closes-Bug: #1523357
Change-Id: Ibb6fb5beabe8b8e5b212825131eba4e03e8964a8

neutron_fwaas/tests/tempest_plugin/tests/scenario/test_fwaas.py

@@ -33,15 +33,14 @@ class TestFWaaS(base.FWaaSScenarioTest):
 
     def _create_server(self, network, security_group=None):
         keys = self.create_keypair()
-        kwargs = {
-            'networks': [
-                {'uuid': network['id']},
-            ],
-            'key_name': keys['name'],
-        }
+        kwargs = {}
         if security_group is not None:
             kwargs['security_groups'] = [{'name': security_group['name']}]
-        server = self.create_server(create_kwargs=kwargs)
+        server = self.create_server(
+            key_name=keys['name'],
+            networks=[{'uuid': network['id']}],
+            wait_until='ACTIVE',
+            **kwargs)
         return server, keys
 
     def _empty_policy(self, server1_ip):