print -> info; end the horror of print vs. print()

Although we could use print() from __future__, this messes
up scripts which use examples as modules.

The simple, if not nicest for 2.7, solution is to use
info(), output() and other mininet.log functions. The disadvantage
is that we may have to adjust things if we change info() to
add automatic newlines, but we can burn that bridge in Mininet
3.x.

examples/scratchnet.py

@@ -41,7 +41,7 @@ def scratchNet( cname='controller', cargs='-v ptcp:' ):
     switch.cmd( 'ovs-vsctl del-br dp0' )
     switch.cmd( 'ovs-vsctl add-br dp0' )
     for intf in switch.intfs.values():
-        print( switch.cmd( 'ovs-vsctl add-port dp0 %s' % intf ) )
+        switch.cmd( 'ovs-vsctl add-port dp0 %s\n' % intf )
 
     # Note: controller and switch are in root namespace, and we
     # can connect via loopback interface