grid: fix distribution_tuple()

 * consider raspbian as a debian
 * never set id

After the change to distro.linux_distribution() in
425f5bb7, raspbian is correctly detected
and id is set, see the execution of both functions on raspbian:

>>> platform.linux_distribution('', '', '', platform._supported_dists, 1)
('debian', '10.11', '')

>>> distro.linux_distribution(full_distribution_name=False)
('raspbian', '10', 'buster')