CORD-48 Fixing filtering rule bug in multi-instance operation.

Change-Id: Ie91b2efcebff1bdb14357b6720ff8214a712cdc2
diff --git a/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/ArpHandler.java b/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/ArpHandler.java
index 55192a9..36563f0 100644
--- a/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/ArpHandler.java
+++ b/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/ArpHandler.java
@@ -35,7 +35,8 @@
 import org.slf4j.LoggerFactory;
 
 import java.nio.ByteBuffer;
-import java.util.List;
+import java.util.Set;
+
 import static com.google.common.base.Preconditions.checkNotNull;
 
 public class ArpHandler {
@@ -112,7 +113,7 @@
 
 
     private boolean isArpReqForRouter(DeviceId deviceId, ARP arpRequest) {
-        List<Ip4Address> gatewayIpAddresses = config.getPortIPs(deviceId);
+        Set<Ip4Address> gatewayIpAddresses = config.getPortIPs(deviceId);
         if (gatewayIpAddresses != null) {
             Ip4Address targetProtocolAddress = Ip4Address.valueOf(arpRequest
                     .getTargetProtocolAddress());