OVS switch connect to controllers using protocols other than TCP like SSL.

Add ability for for OVS switch start connect to controllers using protocols other than TCP.

    net.addController( 'c0', protocol='ssl' )

This now allows OVS to connect to a controller using SSL.  The default of protocol is 'tcp'
as it currently is.  When adding a controller, you specify the protocol and then that value is used during switch.start().  Example and test python script used shown below.

    #!/usr/bin/python
    from mininet.net import Mininet
    from mininet.node import Controller, RemoteController, OVSController
    from mininet.cli import CLI
    from mininet.log import setLogLevel, info
    
    def emptyNet():
        net = Mininet( controller=OVSController )
        net.addController( 'c0',
            cargs='-v pssl:%d -p /etc/openvswitch/ctl-privkey.pem \
                   -c /etc/openvswitch/ctl-cert.pem \
                   -C /var/lib/openvswitch/pki/switchca/cacert.pem',
            protocol='ssl' )
        h1 = net.addHost( 'h1' )
        h2 = net.addHost( 'h2' )
        s1 = net.addSwitch( 's1' )
        net.addLink( h1, s1 )
        net.addLink( h2, s1 )
    
        net.start()
        net.pingAll()
        CLI( net )
        net.stop()
    
    if __name__ == '__main__':
        setLogLevel( 'info' )
        emptyNet()

  Shows OVS listening on SSL.

    root@mininet21:~/SVN/mininet# sudo ovs-vsctl show
    ec21cc9e-4dc3-44d1-8c18-f23409d4615c
        Bridge "s1"
            Controller "ssl:127.0.0.1:6633"
                is_connected: true
            fail_mode: secure
            Port "s1"
                Interface "s1"
                    type: internal
            Port "s1-eth2"
                Interface "s1-eth2"
            Port "s1-eth1"
                Interface "s1-eth1"
        ovs_version: "1.4.6"

Output of script.

    mininet@mininet21:~$ sudo ./ssl2.py
    *** Configuring hosts
    h1 h2
    *** Starting controller
    *** Starting 1 switches
    s1
    *** Ping: testing ping reachability
    h1 -> h2
    h2 -> h1
    *** Results: 0% dropped (2/2 received)
    *** Starting CLI:

  All this assumes that the user setup the SSL keys as described in the FAQ/wiki.