tests/lcitool: fix up indentation to correct style

tests/lcitool: fix up indentation to correct style

3 space indentation snuck into the initial commit. Clean it up before
we let it get established. I've also:

  - removed unused os import
  - added double lines between functions
  - added some comments and grouped and sorted the generation stanzas

My lint tool is also recommending using f-strings but that requires
python 3.6.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Cc: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20220527153603.887929-6-alex.bennee@linaro.org>