Adds default router option only when the gateway is set in subnet.

Change-Id: If14152337a2c1567ea6db16f06f99a50571b55e9
diff --git a/apps/openstacknetworking/app/src/test/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingDhcpHandlerTest.java b/apps/openstacknetworking/app/src/test/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingDhcpHandlerTest.java
index 65331fe..8cd0462 100644
--- a/apps/openstacknetworking/app/src/test/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingDhcpHandlerTest.java
+++ b/apps/openstacknetworking/app/src/test/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingDhcpHandlerTest.java
@@ -77,6 +77,7 @@
 import static org.onlab.packet.DHCP.DHCPOptionCode.OptionCode_END;
 import static org.onlab.packet.DHCP.DHCPOptionCode.OptionCode_MessageType;
 import static org.onlab.packet.DHCP.DHCPOptionCode.OptionCode_RequestedIP;
+import static org.onlab.packet.DHCP.DHCPOptionCode.OptionCode_RouterAddress;
 import static org.onosproject.net.NetTestTools.connectPoint;
 
 /**
@@ -287,6 +288,14 @@
         option.setData(hostRouteByteBuf.array());
         optionList.add(option);
 
+        // default router address setup
+        option = new DhcpOption();
+        option.setCode(OptionCode_RouterAddress.getValue());
+        option.setLength((byte) 4);
+        option.setData(Ip4Address.valueOf(subnet.getGateway()).toOctets());
+        optionList.add(option);
+
+
         // DHCP options end...
         option = new DhcpOption();
         option.setCode(OptionCode_END.getValue());