- Make it compatible with Python 3.
- Install setuptools in a way that's compatible with slapos.rebootstrap
  (otherwise, rebootstrapping fails because signature dependency to
  setuptools changes).

playbook: imt-vm-bootstrap playbook will be called only until success, then it is never called again

This reverts commit 910d2148.

Actually, we will simply stop executing the playbook totally after it is
well configured.

This reverts commit dd750800.

Previously it only worked with Debian 10. This commit reflects the
removal of the apt package 'python-pip' in Debian 11 and the change
of the i2c bus number.

There were still two issues which are solved with this commit:

1. Previously the firewall prevented the installation of Fluentd
   (because no connection via http/https was possible).

2. Previously the sensor couldn't send data to the IoT gateway (
   the opened port wasn't sufficient).

When importing the slapos playbook after running re6stnet-install role,
the user defined computer_name will be ignored and will be overridden
by 'set_facts', line 16 in re6stnet-install/tasks/main.yml. Therefore
the slapos install role is directly called (instead of importing the
playbook) which seems to solve the issue.

(due to activated firewall)

(wrong indentation)

(wasn't possible because of too restrictive ipv6 firewall)

Add restrictive firewall settings to avoid any security risk.

Bug appeared due to wrong pip version. Therefore the version has been
set explicitly.

Now the Python script name is consistent with the file name in the
Fluentd config file as described in the learning track.

Should be installed via rapid.space panel.

Previously it failed because setuptools wasn't installed.

Replaced 'computer_name' with 'computer_id'. Previously I confused both.
Now the user has to enter the respective computer reference.

It won't run in an issue anymore if the file already exists.

Fluentd couldn't be installed because we first have to configure the
SlapOS client via `slapos configure client` before being able to use
`slapos console` (to supply and request Fluentd from a Python script).