Do not rely on notification to enable ovs-usurp-config scripts

With a notification, if chef-client crashes before the end, the script
will never be enabled. Just always enable it, there's no reason why we
would want to not do this in the case where we have the script.

chef/cookbooks/network/recipes/default.rb

@@ -524,8 +524,8 @@ def kill_nic(nic)
       end
       service "ovs-ifup-#{nic.name}" do
         # Don't start it here. It only needs to be executed during boot.
-        action [:nothing]
-        subscribes :enable, resources("template[/etc/init.d/ovs-ifup-#{nic.name}]")
+        action [:enable]
+        only_if { nic.kind_of?(Nic::OvsBridge) }
       end
     end
   end