Cancel DHCP packet request when DHCP relay app is being deactivated

Change-Id: Ic1c10e63471460893865962541806c88fcfdf22d
diff --git a/apps/dhcprelay/src/main/java/org/onosproject/dhcprelay/Dhcp4HandlerImpl.java b/apps/dhcprelay/src/main/java/org/onosproject/dhcprelay/Dhcp4HandlerImpl.java
index 04a9967..7999466 100644
--- a/apps/dhcprelay/src/main/java/org/onosproject/dhcprelay/Dhcp4HandlerImpl.java
+++ b/apps/dhcprelay/src/main/java/org/onosproject/dhcprelay/Dhcp4HandlerImpl.java
@@ -212,8 +212,10 @@
         providerRegistry.unregister(this);
         hostService.removeListener(hostListener);
         defaultServerInfoList.forEach(this::stopMonitoringIps);
+        defaultServerInfoList.forEach(info -> info.getDhcpServerIp4().ifPresent(this::cancelDhcpPacket));
         defaultServerInfoList.clear();
         indirectServerInfoList.forEach(this::stopMonitoringIps);
+        indirectServerInfoList.forEach(info -> info.getDhcpServerIp4().ifPresent(this::cancelDhcpPacket));
         indirectServerInfoList.clear();
     }