Fix ONOS-5091

Change-Id: I11762eb799c1f93536f472807167cdba20a7c8e6
(cherry picked from commit 45f806cc)

@@ -82,7 +82,7 @@ public final class GroupCodec extends JsonCodec<Group> {
                 .put(DEVICE_ID, group.deviceId().toString());
 
         if (group.appId() != null) {
-            result.put(APP_ID, group.appId().toString());
+            result.put(APP_ID, group.appId().name());
         }
 
         if (group.appCookie() != null) {

@@ -62,7 +62,7 @@
     "appId": {
       "type": "string",
       "description": "application identifier",
-      "example": "1"
+      "example": "org.onosproject.rest"
     },
     "appCookie": {
       "type": "string",

@@ -75,7 +75,7 @@
           "appId": {
             "type": "string",
             "description": "application identifier",
-            "example": "1"
+            "example": "org.onosproject.rest"
           },
           "appCookie": {
             "type": "string",

@@ -280,9 +280,9 @@ public class GroupsResourceTest extends ResourceTest {
 
             // check application id
             final String jsonAppId = jsonGroup.get("appId").asString();
-            final String appId = group.appId().toString();
+            final String appId = group.appId().name();
             if (!jsonAppId.equals(appId)) {
-                reason = "appId " + group.appId().toString();
+                reason = "appId " + group.appId().name();
                 return false;
             }