Workaround for the TLSv1 bug in bootstrap

Hi,

When the server is installed in CentOS 6.5, the orchestrator is not able to download the slipstream client package:
```
================================================
=== slipstream-orchestrator bootstrap script ===
================================================
Retrieving the latest version of the SlipStream from: https://slipstream.gnubila.fr/slipstreamclient.tgz
Failed contacting: https://slipstream.gnubila.fr/slipstreamclient.tgz  with error:" <urlopen error [Errno 8] _ssl.c:504: EOF occurred in violation of protocol> " retrying...
Traceback (most recent call last):
  File "/tmp/slipstream.bootstrap", line 409, in <module>
    main()
  File "/tmp/slipstream.bootstrap", line 353, in main
    publishFailureToSlipStreamRun(sys.exc_info())
  File "/tmp/slipstream.bootstrap", line 329, in publishFailureToSlipStreamRun
    _formatException(exc_info))
  File "/tmp/slipstream.bootstrap", line 377, in publish
    self._process_response(self._publish(message))
  File "/tmp/slipstream.bootstrap", line 382, in _publish
    body=message, headers=self._get_headers())
  File "/usr/lib/python2.7/httplib.py", line 958, in request
    self._send_request(method, url, body, headers)
  File "/usr/lib/python2.7/httplib.py", line 992, in _send_request
    self.endheaders(body)
  File "/usr/lib/python2.7/httplib.py", line 954, in endheaders
    self._send_output(message_body)
  File "/usr/lib/python2.7/httplib.py", line 814, in _send_output
    self.send(msg)
  File "/usr/lib/python2.7/httplib.py", line 776, in send
    self.connect()
  File "/usr/lib/python2.7/httplib.py", line 1161, in connect
    self.sock = ssl.wrap_socket(sock, self.key_file, self.cert_file)
  File "/usr/lib/python2.7/ssl.py", line 381, in wrap_socket
    ciphers=ciphers)
  File "/usr/lib/python2.7/ssl.py", line 143, in __init__
    self.do_handshake()
  File "/usr/lib/python2.7/ssl.py", line 305, in do_handshake
    self._sslobj.do_handshake()
ssl.SSLError: [Errno 8] _ssl.c:504: EOF occurred in violation of protocol
```

This modification fix the problem y forcing SSLv3 protocol (as it was already done for the wget commands)

Best,
Jerome