ONOS-2184 Adding VirtualHost support in Virtual Networks.

Change-Id: I1318f20a9b14f1f99dc8eb48b9660a208165bac1
diff --git a/incubator/api/src/main/java/org/onosproject/incubator/net/virtual/VirtualNetworkService.java b/incubator/api/src/main/java/org/onosproject/incubator/net/virtual/VirtualNetworkService.java
index ebe0b69..530c67a 100644
--- a/incubator/api/src/main/java/org/onosproject/incubator/net/virtual/VirtualNetworkService.java
+++ b/incubator/api/src/main/java/org/onosproject/incubator/net/virtual/VirtualNetworkService.java
@@ -51,6 +51,15 @@
     Set<VirtualDevice> getVirtualDevices(NetworkId networkId);
 
     /**
+     * Returns a collection of all virtual hosts in the specified network.
+     *
+     * @param networkId network identifier
+     * @return collection of hosts
+     * @throws org.onlab.util.ItemNotFoundException if no such network found
+     */
+    Set<VirtualHost> getVirtualHosts(NetworkId networkId);
+
+    /**
      * Returns collection of all virtual links in the specified network.
      *
      * @param networkId network identifier