python3: skip test_concurrent_futures/test_deadlock

These tests are causing hangs on the Autobuilder, so disable them for
now.

Signed-off-by: Trevor Gamblin <tgamblin@baylibre.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 291f3780)
Signed-off-by: Steve Sakoman <steve@sakoman.com>