Improve log message of DHCP relay

Change-Id: Ibd353647ca5cfa93c8bf42183ad5490070d64e53
(cherry picked from commit 1b20123ed8e7d8347c2f2f05e23f64bf76f80060)
diff --git a/apps/dhcprelay/src/main/java/org/onosproject/dhcprelay/DhcpRelay.java b/apps/dhcprelay/src/main/java/org/onosproject/dhcprelay/DhcpRelay.java
index 273e32b..85bf31c 100644
--- a/apps/dhcprelay/src/main/java/org/onosproject/dhcprelay/DhcpRelay.java
+++ b/apps/dhcprelay/src/main/java/org/onosproject/dhcprelay/DhcpRelay.java
@@ -287,12 +287,11 @@
 
         //process the dhcp packet before sending to server
         private void processDhcpPacket(PacketContext context, DHCP dhcpPayload) {
-
-            Set<Interface> clientServerInterfaces = interfaceService.
-                    getInterfacesByPort(context.inPacket().receivedFrom());
+            ConnectPoint inPort = context.inPacket().receivedFrom();
+            Set<Interface> clientServerInterfaces = interfaceService.getInterfacesByPort(inPort);
             //ignore the packets if dhcp client interface is not configured on onos.
             if (clientServerInterfaces.isEmpty()) {
-                log.warn("client virtual interface not configured");
+                log.warn("Virtual interface is not configured on {}", inPort);
                 return;
             }