Bug 21190: Prepare Log.t for further changes

Bug 21190: Prepare Log.t for further changes

This patch only makes cosmetic changes:
[1] It moves the existing tests at 'root level' inside a new subtest.
[2] It obviously adds indentation for step 1.
[3] It fixes some whitespace (tabs, space before newline)

Test plan:
Run t/db../Log.t

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jon Knight <J.P.Knight@lboro.ac.uk>
Signed-off-by: Michal Denar <black23@gmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>