Unit tests for the distributed group store.

Change-Id: Ie8f00b9bbc1ba46a6f80e70f63d1fd853d64154b
diff --git a/core/store/dist/src/main/java/org/onosproject/store/group/impl/DistributedGroupStore.java b/core/store/dist/src/main/java/org/onosproject/store/group/impl/DistributedGroupStore.java
index a0cb189..cd42b17 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/group/impl/DistributedGroupStore.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/group/impl/DistributedGroupStore.java
@@ -1014,7 +1014,7 @@
     /**
      * Flattened map key to be used to store group entries.
      */
-    private class GroupStoreMapKey {
+    protected static class GroupStoreMapKey {
         private final DeviceId deviceId;
 
         public GroupStoreMapKey(DeviceId deviceId) {
@@ -1047,7 +1047,7 @@
         }
     }
 
-    private class GroupStoreKeyMapKey extends GroupStoreMapKey {
+    protected static class GroupStoreKeyMapKey extends GroupStoreMapKey {
         private final GroupKey appCookie;
         public GroupStoreKeyMapKey(DeviceId deviceId,
                                    GroupKey appCookie) {
@@ -1078,7 +1078,7 @@
         }
     }
 
-    private class GroupStoreIdMapKey extends GroupStoreMapKey {
+    protected static class GroupStoreIdMapKey extends GroupStoreMapKey {
         private final GroupId groupId;
         public GroupStoreIdMapKey(DeviceId deviceId,
                                   GroupId groupId) {