Replaced IpPrefix and IpAddress in the following methods
and cleanup related code:

 - Host.ipAddresses()
 - DefaultHost.ipAddresses()
 - HostDescription.ipAddress()
 - DefaultHostDescription.ipAddress()
 - HostService.getHostsByIp()
 - HostManager.getHostsByIp()
 - HostStore.getHosts()
 - GossipHostStore.getHosts()
 - SimpleHostStore.getHosts()
 - ProxyArpService.known()
 - ProxyArpManager.known()

As a result of the above cleanup, the "hosts" CLI command outputs
the IP addresses as "1.2.3.4" instead of "1.2.3.4/32".

Also, the following REST calls might be affected as well with
the above format replacement:
  - REST POST: config/topology
  - REST GET: topology/graph
diff --git a/apps/tvue/src/main/java/org/onlab/onos/tvue/TopologyResource.java b/apps/tvue/src/main/java/org/onlab/onos/tvue/TopologyResource.java
index 686455b..cc03459 100644
--- a/apps/tvue/src/main/java/org/onlab/onos/tvue/TopologyResource.java
+++ b/apps/tvue/src/main/java/org/onlab/onos/tvue/TopologyResource.java
@@ -34,7 +34,7 @@
 import org.onlab.onos.net.topology.TopologyGraph;
 import org.onlab.onos.net.topology.TopologyService;
 import org.onlab.onos.net.topology.TopologyVertex;
-import org.onlab.packet.IpPrefix;
+import org.onlab.packet.IpAddress;
 import org.onlab.rest.BaseResource;
 
 import javax.ws.rs.GET;
@@ -92,8 +92,8 @@
         // Merge the exterior and interior vertexes and inject host links as
         // the exterior edges.
         for (Host host : hostService.getHosts()) {
-            Set<IpPrefix> ipAddresses = host.ipAddresses();
-            IpPrefix ipAddress = ipAddresses.isEmpty() ? null : ipAddresses.iterator().next();
+            Set<IpAddress> ipAddresses = host.ipAddresses();
+            IpAddress ipAddress = ipAddresses.isEmpty() ? null : ipAddresses.iterator().next();
             String label = ipAddress != null ? ipAddress.toString() : host.mac().toString();
             vertexesNode.add(json(mapper, host.id(), 3, label, true));
             edgesNode.add(json(mapper, 1, host.location(), new ConnectPoint(host.id(), portNumber(-1))));