support/testing: add python-twisted tests

support/testing: add python-twisted tests

Use a minimal script to listen to a port and check using netstat.

Signed-off-by: Ricardo Martincoski <ricardo.martincoski@gmail.com>
Cc: Asaf Kahlon <asafka7@gmail.com>
Cc: Yegor Yefremov <yegorslists@googlemail.com>
Reviewed-by: Yegor Yefremov <yegorslists@googlemail.com>
[Thomas: increase the delay after starting the Twisted server, as 5
seconds was not enough for Python 3.x configurations.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>