Ports and port description are not cleared up properly upon removal

Change-Id: I4a2287e9ed29c9a423d7ae297c12736537191619
(cherry picked from commit f198430fee8d188a8704f0cc06f403f10df70c3a)
diff --git a/core/store/dist/src/main/java/org/onosproject/store/device/impl/DeviceDescriptions.java b/core/store/dist/src/main/java/org/onosproject/store/device/impl/DeviceDescriptions.java
index f14b062..bcebc61 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/device/impl/DeviceDescriptions.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/device/impl/DeviceDescriptions.java
@@ -104,4 +104,13 @@
         }
         portDescs.put(newOne.value().portNumber(), newOne);
     }
+
+    /**
+     * Removes PortDescription.
+     *
+     * @param portNumber the port to remove.
+     */
+    public void removePortDesc(PortNumber portNumber) {
+        portDescs.remove(portNumber);
+    }
 }