Implement OpenVPN test

Test that OpenVPN is working properly.

The test must:

• Establish a connection to an OpenVPN server.
• Check that the connection is successful or if it fails to connect to the server.
• Check that is possible to make an HTTP to a web server listening on the VPN network.

Open questions are:

• Which could be the possible failures connection to an OpenVPN server?
• What debug information can we get that would allow us to understand why and how OpenVPN is being blocked ?