Check neutron agent extension support in Info page

Some neutron plugin don't support agent extension, and
Horizon show 404 error on admin info page.
In this commit, we are going to add check if agent
extension supported or not.
Closes-bug: 1331032

Change-Id: I5cd3ec747c650fc2b826d55f39be618eca1b7caa

openstack_dashboard/api/neutron.py

@@ -859,6 +859,10 @@ def is_security_group_extension_supported(request):
     return is_extension_supported(request, 'security-group')
 
 
+def is_agent_extension_supported(request):
+    return is_extension_supported(request, 'agent')
+
+
 # Using this mechanism till a better plugin/sub-plugin detection
 # mechanism is available.
 # Using local_settings to detect if the "router" dashboard

openstack_dashboard/dashboards/admin/info/tabs.py

@@ -85,7 +85,8 @@ class NetworkAgentsTab(tabs.TableTab):
     template_name = constants.INFO_DETAIL_TEMPLATE_NAME
 
     def allowed(self, request):
-        return base.is_service_enabled(request, 'network')
+        return (base.is_service_enabled(request, 'network') and
+                neutron.is_agent_extension_supported(request))
 
     def get_network_agents_data(self):
         try:

openstack_dashboard/dashboards/admin/info/tests.py

@@ -32,6 +32,8 @@ class SystemInfoViewTests(test.BaseAdminViewTests):
     def test_index(self):
         services = self.services.list()
         api.nova.service_list(IsA(http.HttpRequest)).AndReturn(services)
+        api.neutron.is_extension_supported(IsA(http.HttpRequest),
+                                           'agent').AndReturn(True)
         agents = self.agents.list()
         api.neutron.agent_list(IsA(http.HttpRequest)).AndReturn(agents)
 
@@ -83,6 +85,8 @@ class SystemInfoViewTests(test.BaseAdminViewTests):
                 .MultipleTimes().AndReturn(True)
         api.nova.default_quota_get(IsA(http.HttpRequest),
                                    IgnoreArg()).AndReturn({})
+        api.neutron.is_extension_supported(IsA(http.HttpRequest),
+                                           'agent').AndReturn(True)
         api.neutron.is_extension_supported(IsA(http.HttpRequest),
                                            'security-group').AndReturn(True)
 
@@ -128,9 +132,12 @@ class SystemInfoViewTests(test.BaseAdminViewTests):
 
         if neutron_enabled:
             self.mox.StubOutWithMock(api.neutron, 'agent_list')
+            self.mox.StubOutWithMock(api.neutron, 'is_extension_supported')
+            api.neutron.is_extension_supported(IsA(http.HttpRequest),
+                                               'agent').AndReturn(True)
+
             api.neutron.agent_list(IsA(http.HttpRequest)).AndReturn([])
 
-            self.mox.StubOutWithMock(api.neutron, 'is_extension_supported')
             api.neutron.is_extension_supported(IsA(http.HttpRequest),
                             'security-group').AndReturn(neutron_sg_enabled)