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/cli/CordVtnFlushRules.java b/src/main/java/org/onosproject/cordvtn/cli/CordVtnFlushRules.java
index f428ea4..228d06c 100644
--- a/src/main/java/org/onosproject/cordvtn/cli/CordVtnFlushRules.java
+++ b/src/main/java/org/onosproject/cordvtn/cli/CordVtnFlushRules.java
@@ -18,7 +18,7 @@
 
 import org.apache.karaf.shell.commands.Command;
 import org.onosproject.cli.AbstractShellCommand;
-import org.onosproject.cordvtn.impl.CordVtnNodeManager;
+import org.onosproject.cordvtn.impl.CordVtnPipeline;
 
 /**
  * Deletes nodes from the service.
@@ -29,8 +29,8 @@
 
     @Override
     protected void execute() {
-        CordVtnNodeManager nodeManager = AbstractShellCommand.get(CordVtnNodeManager.class);
-        nodeManager.flushRules();
+        CordVtnPipeline pipeline = AbstractShellCommand.get(CordVtnPipeline.class);
+        pipeline.flushRules();
         print("Successfully flushed");
     }
 }