Refactored to handle service instance by service type

- Added service instance handler
- Implemented dummy, vsg, and olt agent instance handler

Change-Id: Id3edd5eecb1caadf0f835cb10a952100e18b283b
diff --git a/src/main/java/org/onosproject/cordvtn/impl/service/DummyInstanceHandler.java b/src/main/java/org/onosproject/cordvtn/impl/service/DummyInstanceHandler.java
new file mode 100644
index 0000000..ee78218
--- /dev/null
+++ b/src/main/java/org/onosproject/cordvtn/impl/service/DummyInstanceHandler.java
@@ -0,0 +1,57 @@
+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.cordvtn.impl.service;
+
+import org.apache.felix.scr.annotations.Activate;
+import org.apache.felix.scr.annotations.Component;
+
+import org.apache.felix.scr.annotations.Deactivate;
+import org.onosproject.cordvtn.api.Instance;
+import org.onosproject.cordvtn.api.InstanceHandler;
+import org.onosproject.cordvtn.impl.CordVtnInstanceHandler;
+import org.onosproject.xosclient.api.VtnService;
+
+import static java.util.concurrent.Executors.newSingleThreadScheduledExecutor;
+import static org.onlab.util.Tools.groupedThreads;
+
+/**
+ * Provides network connectivity for dummy service instances.
+ */
+@Component(immediate = true)
+public class DummyInstanceHandler extends CordVtnInstanceHandler implements InstanceHandler {
+
+    @Activate
+    protected void activate() {
+        serviceType = VtnService.ServiceType.DUMMY;
+        eventExecutor = newSingleThreadScheduledExecutor(groupedThreads("onos/cordvtn-dummy", "event-handler"));
+        super.activate();
+    }
+
+    @Deactivate
+    protected void deactivate() {
+        super.deactivate();
+    }
+
+    @Override
+    public void instanceDetected(Instance instance) {
+        super.instanceDetected(instance);
+    }
+
+    @Override
+    public void instanceRemoved(Instance instance) {
+        super.instanceRemoved(instance);
+    }
+}