Disable VPNaaS functional tests in the neutronclient gate

This addresses failures for neutronclient's functional job of
advanced services. VPNaaS is no longer maintained and thus it
makes sense to stop gating against it. Hook and tests are kept
for local development and in case things will resurrect back
to life.

This patch also makes extension functional tests conditional to
the presence of the extension under test.

Closes-bug: #1645819

Conflicts:
        neutronclient/tests/functional/base.py

Change-Id: I17ab8accaa943b9ac04893b5e131be0afe0f5429
(cherry picked from commit a0f15a84d7)

neutronclient/tests/functional/adv-svcs/test_readonly_neutron_fwaas.py

@@ -13,10 +13,15 @@
 from neutronclient.tests.functional import base
 
 
-class SimpleReadOnlyNeutronClientTest(base.ClientTestBase):
+class SimpleReadOnlyNeutronFwv1ClientTest(base.ClientTestBase):
 
     """Tests for FWaaS v1 based client commands that are read only"""
 
+    def setUp(self):
+        super(SimpleReadOnlyNeutronFwv1ClientTest, self).setUp()
+        if not self.is_extension_enabled('fwaas'):
+            self.skipTest('FWaaS is not enabled')
+
     def test_neutron_firewall_list(self):
         firewall_list = self.parser.listing(self.neutron
                                             ('firewall-list'))

neutronclient/tests/functional/adv-svcs/test_readonly_neutron_vpn.py

@@ -25,6 +25,10 @@ class SimpleReadOnlyNeutronVpnClientTest(base.ClientTestBase):
     * with and without optional parameters
     * initially just check return codes, and later test command outputs
     """
+    def setUp(self):
+        super(SimpleReadOnlyNeutronVpnClientTest, self).setUp()
+        if not self.is_extension_enabled('vpnaas'):
+            self.skipTest('VPNaaS is not enabled')
 
     def test_neutron_vpn_ikepolicy_list(self):
         ikepolicy = self.parser.listing(self.neutron('vpn-ikepolicy-list'))

neutronclient/tests/functional/base.py

@@ -63,3 +63,10 @@ class ClientTestBase(base.ClientTestBase):
     def neutron(self, *args, **kwargs):
         return self.clients.neutron(*args,
                                     **kwargs)
+
+    def is_extension_enabled(self, extension_alias):
+        extensions = self.parser.listing(self.neutron('ext-list'))
+        for extension in extensions:
+            if extension_alias in extension['alias']:
+                return True
+        return False

neutronclient/tests/functional/hooks/gate_hook.sh

@@ -22,7 +22,6 @@ ${config}
 if [ "$VENV" == "functional-adv-svcs" ]
 then
     load_rc_hook fwaas
-    load_rc_hook vpnaas
 fi
 
 $BASE/new/devstack-gate/devstack-vm-gate.sh