It was pretty nasty how original LXD connection was designed. It is ok
to just wrap that to class and pass it around instead of calling
connection from various locations just to be sure that all is
initialized before we use it.

This is arguably better than raising NotImplementedError. It also
catches inconsistencies much sooner.

This is now only initial implementation. There should be also
specification of board and more but that is going to be added later on
once we are able to run tests on more than one board.

It is planned to have not only tests but also selftests and for that we
do not need configuration. Those arguments are solely for real tests.
Moving them to tests makes them required to only ten those tests.

First network test in set was in some probability failing. This just
adds dummy sleep to stabilize network before tests are executed.

This also incorporates feedback from ongoing review.

This reuses WAN tests for LAN as well to check that clients are able to
access internet trough router.

Watchdog is not running immeediatelly after boot as it seems and also it
is not essential for use at the moment to check for it.

Some of the non-essential fixtures should be scoped not for session but
for module only or even less because they can collide with other tests.

These are simple tests to check system that was just booted.

Static method can't be used this way. The only other clean alternative
is just changing it from method to function.

Upper case are constants and we do not consider these as constants so we
should not name them that way.

Fix of typo nsfram vs nsfarm

It makes no sense as we reset access rights either way. Let's just check
if it is standard file and that is it.

The problem with assert based implementation is that we are missing
crucial information like what was in output in error message. This just
let's pexpect throw exception and that is fine.