Do not try to show L3 agent action when enable_router is False

When enable_router settings is False, 'routers' panel is not
registered and URL resolver of L3 agent action in the network
agent table will result in a failure.
As a result, System Information panel cannot be displayed.

This commit adds a check whether the router panel is enabled or not.

Change-Id: I67aba79f61870b093d4c1d9c7527003704483d50
Closes-Bug: #1671785

openstack_dashboard/dashboards/admin/info/tables.py

@@ -10,6 +10,7 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+from django.conf import settings
 from django.core import urlresolvers
 from django import template
 from django.template import defaultfilters as filters
@@ -179,6 +180,9 @@ class NetworkL3AgentRoutersLinkAction(tables.LinkAction):
     verbose_name = _("View Routers")
 
     def allowed(self, request, datum):
+        network_config = getattr(settings, 'OPENSTACK_NEUTRON_NETWORK', {})
+        if not network_config.get('enable_router', True):
+            return False
         # Determine whether this action is allowed for the current request.
         return datum.agent_type == "L3 agent"