Allow tests to get control of the terminal

[vkarak]

Sometimes a test my need to use sudo to run a command. This currently fails, as stdin is set to /dev/null when we spawn processes. Reading from stdin is not an option as well, as this would imply that somebody would have to give their password in plain text. Ideally, we would like for such programs to get control of the terminal and get their input. I have no idea if this is possible, but I'm recording it as a nice to have feature.