fix the problem of "no tty to run sudo"

When start Tachyon with "all SudoMount" options, the problem may come out with "sudo: sorry, you must have a tty to run sudo" or "no tty present and no askpass program specified". It's because the 'tachyon-start.sh' runs a sudo command in a ssh script (For example, you can simply run 'ssh localhost sudo ls' and get the problem).
And here, the problem can be fixed with the '-t' option of ssh.