[lib/gen/reference-api] Fix the case where kavlan is disabled on a cluster (for ruby 2.1.5)

lib/refrepo/gen/reference-api.rb

@@ -307,7 +307,7 @@ def generate_reference_api
               end
             end
             # If kavlan entry is not defined here, set it node's kavlan description
-            network_adapter["kavlan"] ||= node["kavlan"].keys.include?(network_adapter["device"]) ? true : false rescue false
+            network_adapter["kavlan"] ||= node["kavlan"].nil? ? false : node["kavlan"].keys.include?(network_adapter["device"]) ? true : false
 
             network_adapter.delete("network_address") if network_adapter["network_address"] == 'none'
           }