Bug 21190: Add subtest to Log.t for GDPR logging

Bug 21190: Add subtest to Log.t for GDPR logging

Apart from a new subtest, doing some more cleanup:
[1] Copyright statement
[2] Removing the (unneeded) flush
[3] Removing C4::Log from the BEGIN block; we seem to skip that nowadays.
[4] $succes goes to the subtest, $schema and $dbh are global our vars.
    Not required but just what we should do if it would run under Plack.

Test plan:
Run t/db_dependent/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>