onos.py: compute hazelcast interface based on IP address

Change-Id: Ifadfaed81f3febd0a4644a763092e19672746e37
diff --git a/tools/test/topos/onos.py b/tools/test/topos/onos.py
index 18f2212..69aa205 100755
--- a/tools/test/topos/onos.py
+++ b/tools/test/topos/onos.py
@@ -97,13 +97,17 @@
         self.terminate()
 
     def updateHazelcast( self ):
+        hz = '192.168.123.*'
+        if self.ip is not None:
+            hz = '.'.join(self.ip.split('.')[:-1]) + '.*'
+
         readfile = self.karafDir + 'etc/hazelcast.xml'
         writefile = self.instanceDir + 'etc/hazelcast.xml'
         with open( readfile, 'r' ) as r:
             with open( writefile, 'w' ) as w:
                 for line in r.readlines():
                     if '<interface>' in line:
-                        line = '<interface>' + '192.168.123.*' + '</interface>\n'
+                        line = '<interface>' + hz + '</interface>\n'
                     w.write( line )
 
     def updateFeatures( self ):