VOL-1598 Add new group API in OpenOLT Driver

A new API method called PerformGroupOperation is added. This method
performs the corresponding group operation according to the command
field of the Group message. The method currently assumes fixed queue
QoS model. FlowAdd_ and FlowRemove_ are also updated accordingly.

Change-Id: I355f20c3b5b5df484e90082936b10386b5fdf67f
diff --git a/agent/common/server.cc b/agent/common/server.cc
index 1c67137..e33938b 100644
--- a/agent/common/server.cc
+++ b/agent/common/server.cc
@@ -140,7 +140,8 @@
             request->classifier(),
             request->action(),
             request->priority(),
-            request->cookie());
+            request->cookie(),
+            request->group_id());
     }
 
     Status FlowRemove(
@@ -300,6 +301,12 @@
         return Status::OK;
     };
 
+    Status PerformGroupOperation(
+            ServerContext* context,
+            const openolt::Group* request,
+            openolt::Empty* response) override {
+        return PerformGroupOperation_(request);
+    };
 };
 
 void RunServer() {