nixos tests: waitUntilTTYMatches: Log TTY contents on last try

If the test has not passed yet, on the last attempt it now outputs:

    machine: Last chance to match /logine: / on TTY2, which currently contains:
    machine: running command: fold -w$(stty -F /dev/tty2 size | awk '{print $2}') /dev/vcs2
    machine: exit status 0
    machine:

    <<< Welcome to NixOS 17.09.git.a804ef4 (x86_64) - tty2 >>>

    machine login:

to help debug the problem. Notice the "logine" typo in my check.