Re-order checks in networking auto-detection

To support OVS to OVN migration checks we want the basic overcloud
configure job to set up N-OVS and/or N-GW when present and the
OVN pre migration configure job will copy the configuration for us.

unit_tests/utilities/test_zaza_utilities_openstack.py

@@ -1227,6 +1227,13 @@ class TestOpenStackUtils(ut_utils.BaseTestCase):
         self.get_application.side_effect = [KeyError, KeyError]
         self.assertFalse(openstack_utils.ovn_present())
 
+    def test_ngw_present(self):
+        self.patch_object(openstack_utils.model, 'get_application')
+        self.get_application.side_effect = None
+        self.assertTrue(openstack_utils.ngw_present())
+        self.get_application.side_effect = KeyError
+        self.assertFalse(openstack_utils.ngw_present())
+
     def test_configure_gateway_ext_port(self):
         # FIXME: this is not a complete unit test for the function as one did
         # not exist at all I'm adding this to test one bit and we'll add more
@@ -1234,10 +1241,12 @@ class TestOpenStackUtils(ut_utils.BaseTestCase):
         self.patch_object(openstack_utils, 'deprecated_external_networking')
         self.patch_object(openstack_utils, 'dvr_enabled')
         self.patch_object(openstack_utils, 'ovn_present')
+        self.patch_object(openstack_utils, 'ngw_present')
         self.patch_object(openstack_utils, 'get_gateway_uuids')
         self.patch_object(openstack_utils, 'get_admin_net')
-        self.dvr_enabled = False
-        self.ovn_present = False
+        self.dvr_enabled.return_value = False
+        self.ovn_present.return_value = False
+        self.ngw_present.return_value = True
         self.get_admin_net.return_value = {'id': 'fakeid'}
 
         novaclient = mock.MagicMock()

zaza/openstack/utilities/openstack.py

@@ -554,6 +554,20 @@ def dvr_enabled():
     return get_application_config_option('neutron-api', 'enable-dvr')
 
 
+def ngw_present():
+    """Check whether Neutron Gateway is present in deployment.
+
+    :returns: True when Neutron Gateway is present, False otherwise
+    :rtype: bool
+    """
+    try:
+        model.get_application('neutron-gateway')
+        return True
+    except KeyError:
+        pass
+    return False
+
+
 def ovn_present():
     """Check whether OVN is present in deployment.
 
@@ -721,6 +735,9 @@ def configure_gateway_ext_port(novaclient, neutronclient, net_id=None,
         except KeyError:
             # neutron-gateway not in deployment
             pass
+    elif ngw_present():
+        uuids = itertools.islice(get_gateway_uuids(), limit_gws)
+        application_names = ['neutron-gateway']
     elif ovn_present():
         uuids = itertools.islice(get_ovn_uuids(), limit_gws)
         application_names = ['ovn-chassis']
@@ -735,8 +752,7 @@ def configure_gateway_ext_port(novaclient, neutronclient, net_id=None,
         config.update({'ovn-bridge-mappings': 'physnet1:br-ex'})
         add_dataport_to_netplan = True
     else:
-        uuids = itertools.islice(get_gateway_uuids(), limit_gws)
-        application_names = ['neutron-gateway']
+        raise RuntimeError('Unable to determine charm network topology.')
 
     if not net_id:
         net_id = get_admin_net(neutronclient)['id']