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/core/net/src/test/java/org/onlab/onos/net/host/impl/HostManagerTest.java b/core/net/src/test/java/org/onlab/onos/net/host/impl/HostManagerTest.java
index c20da19..67e6cc4 100644
--- a/core/net/src/test/java/org/onlab/onos/net/host/impl/HostManagerTest.java
+++ b/core/net/src/test/java/org/onlab/onos/net/host/impl/HostManagerTest.java
@@ -58,8 +58,8 @@
     private static final HostId HID1 = HostId.hostId(MAC1, VLAN1);
     private static final HostId HID2 = HostId.hostId(MAC2, VLAN1);
 
-    private static final IpPrefix IP1 = IpPrefix.valueOf("10.0.0.1");
-    private static final IpPrefix IP2 = IpPrefix.valueOf("10.0.0.2");
+    private static final IpAddress IP1 = IpAddress.valueOf("10.0.0.1");
+    private static final IpAddress IP2 = IpAddress.valueOf("10.0.0.2");
 
     private static final DeviceId DID1 = DeviceId.deviceId("of:001");
     private static final DeviceId DID2 = DeviceId.deviceId("of:002");
@@ -115,7 +115,7 @@
     }
 
     private void detect(HostId hid, MacAddress mac, VlanId vlan,
-                        HostLocation loc, IpPrefix ip) {
+                        HostLocation loc, IpAddress ip) {
         HostDescription descr = new DefaultHostDescription(mac, vlan, loc, ip);
         providerService.hostDetected(hid, descr);
         assertNotNull("host should be found", mgr.getHost(hid));