Implementing region hosts for topology 2

Change-Id: I6d1e45b1152b2387d4ff981dc0666868235eb1c3
diff --git a/core/net/src/main/java/org/onosproject/net/region/impl/RegionManager.java b/core/net/src/main/java/org/onosproject/net/region/impl/RegionManager.java
index 81a9dfa..75d96ed 100644
--- a/core/net/src/main/java/org/onosproject/net/region/impl/RegionManager.java
+++ b/core/net/src/main/java/org/onosproject/net/region/impl/RegionManager.java
@@ -25,6 +25,7 @@
 import org.onosproject.cluster.NodeId;
 import org.onosproject.event.AbstractListenerManager;
 import org.onosproject.net.DeviceId;
+import org.onosproject.net.HostId;
 import org.onosproject.net.region.Region;
 import org.onosproject.net.region.RegionAdminService;
 import org.onosproject.net.region.RegionEvent;
@@ -149,4 +150,11 @@
         return store.getRegionDevices(regionId);
     }
 
+    @Override
+    public Set<HostId> getRegionHosts(RegionId regionId) {
+        checkPermission(REGION_READ);
+        checkNotNull(regionId, REGION_ID_NULL);
+        return store.getRegionHosts(regionId);
+    }
+
 }