support/testing: add python-django test

This test comprises of four simple steps:
  1: Start a new simple project called testsite.
  2: Run ./manage.py migrate on the new testsite.
  3: Run ./manage.py runserver 0.0.0.0:1234 & sleep 30
    - The sleep 30 is necessary as it may take several seconds for
      the django server to fully start.
  4: Run netstat to ensure the server opened port 1234.

Signed-off-by: Adam Duskett <aduskett@greenlots.com>
[Thomas: use self.assertRunOk() when appropriate]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>