Switch QA to tty-less mode

This makes ssh generate much less noise when QA is run itself without
a tty, as otherwise we get thousands of lines of:

  Pseudo-terminal will not be allocated because stdin is not a terminal.

in the QA logs (which are already big enough).

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: René Nussbaumer <rn@google.com>