Handle Fedora's telnet output:

----------
*** c0 : ('echo A | telnet -e A 127.0.0.1 6633',)
telnet: connect to address 127.0.0.1: Connection refused
Telnet escape character is 'A'.
Trying 127.0.0.1...
Unable to contact the remote controller at 127.0.0.1:6633
----------

mininet/node.py

@@ -1140,7 +1140,7 @@ def checkListening( self ):
                              "installed." )
         listening = self.cmd( "echo A | telnet -e A %s %d" %
                               ( self.ip, self.port ) )
-        if 'Unable' not in listening:
+        if 'refused' not in listening:
             servers = self.cmd( 'netstat -atp' ).split( '\n' )
             pstr = ':%d ' % self.port
             clist = servers[ 0:1 ] + [ s for s in servers if pstr in s ]
@@ -1235,6 +1235,6 @@ def checkListening( self ):
         "Warn if remote controller is not accessible"
         listening = self.cmd( "echo A | telnet -e A %s %d" %
                               ( self.ip, self.port ) )
-        if 'Unable' in listening:
+        if 'refused' in listening:
             warn( "Unable to contact the remote controller"
                   " at %s:%d\n" % ( self.ip, self.port ) )