[ONOS-6610] Tests for NetconfDeviceProvider InternalDeviceListener

Change-Id: I13921ddc0aaed27f7428060780c06c1fa149fa29
diff --git a/providers/netconf/device/src/main/java/org/onosproject/provider/netconf/device/impl/NetconfDeviceProvider.java b/providers/netconf/device/src/main/java/org/onosproject/provider/netconf/device/impl/NetconfDeviceProvider.java
index b30c6a0..7a31150 100644
--- a/providers/netconf/device/src/main/java/org/onosproject/provider/netconf/device/impl/NetconfDeviceProvider.java
+++ b/providers/netconf/device/src/main/java/org/onosproject/provider/netconf/device/impl/NetconfDeviceProvider.java
@@ -141,7 +141,7 @@
                     "default is 30 sec")
     private int pollFrequency = DEFAULT_POLL_FREQUENCY_SECONDS;
 
-    protected final ExecutorService executor =
+    protected ExecutorService executor =
             Executors.newFixedThreadPool(5, groupedThreads("onos/netconfdeviceprovider",
                                                            "device-installer-%d", log));
     protected ScheduledExecutorService connectionExecutor