Put configs back to pending state when the config factory is removed.

Addresses one of the causes of ONOS-4605 - not sure if there are others.

Change-Id: I2897e84a10b13ac00d5a03c31b7a08daae57d8cb

@@ -166,10 +166,22 @@ public class DistributedNetworkConfigStore
     @Override
     public void removeConfigFactory(ConfigFactory configFactory) {
         factoriesByConfig.remove(configFactory.configClass().getName());
+        processExistingConfigs(configFactory);
         notifyDelegate(new NetworkConfigEvent(CONFIG_UNREGISTERED, configFactory.configKey(),
                                               configFactory.configClass()));
     }
 
+    // Sweep through any configurations for the config factory, set back to pending state.
+    private void processExistingConfigs(ConfigFactory configFactory) {
+        ImmutableSet.copyOf(configs.keySet()).forEach(k -> {
+            if (Objects.equals(configFactory.configClass().getName(), k.configClass)) {
+                JsonNode json = configs.remove(k).value();
+                configs.put(key(k.subject, configFactory.configKey()), json);
+                log.debug("Set config pending: {}, {}", k.subject, k.configClass);
+            }
+        });
+    }
+
     @Override
     @SuppressWarnings("unchecked")
     public <S, C extends Config<S>> ConfigFactory<S, C> getConfigFactory(Class<C> configClass) {