Update host's IP address during name-IP substitution

fixes #139

mininet/cli.py

@@ -321,7 +321,7 @@ def default( self, line ):
         if first in self.nodemap:
             node = self.nodemap[ first ]
             # Substitute IP addresses for node names in command
-            rest = [ self.nodemap[ arg ].IP()
+            rest = [ self.nodemap[ arg ].defaultIntf().updateIP()
                      if arg in self.nodemap else arg
                      for arg in rest ]
             rest = ' '.join( rest )