Add listner for down paths to path painter App and highlights remove when changing overlay

Change-Id: I1bf94468a61bd1a7211532a5b8e9e6cdfbecbda5
diff --git a/apps/pathpainter/src/main/java/org/onosproject/pathpainter/PathPainterTopovOverlay.java b/apps/pathpainter/src/main/java/org/onosproject/pathpainter/PathPainterTopovOverlay.java
index 47ae0d3..78f5f90 100644
--- a/apps/pathpainter/src/main/java/org/onosproject/pathpainter/PathPainterTopovOverlay.java
+++ b/apps/pathpainter/src/main/java/org/onosproject/pathpainter/PathPainterTopovOverlay.java
@@ -37,6 +37,12 @@
     }
 
     @Override
+    public void deactivate() {
+        super.deactivate();
+        log.debug("PathPainterOverlay Deactivated");
+    }
+
+    @Override
     public void modifyDeviceDetails(PropertyPanel pp, DeviceId deviceId) {
         pp.addButton(SRC_BUTTON).addButton(DST_BUTTON);
     }