Bug 19169: Add a test to detect unneeded 'atomicupdate' files

Bug 19169: Add a test to detect unneeded 'atomicupdate' files

to test...

1/ set git repo
    $ git reset --hard v21.11.03

2/ run test
    $ prove ./t
    OK

3/ apply patch

4/ run test again, observe FAIL

    $ prove ./t/00-check-atomic-updates.pl
    ./t/00-check-atomic-updates.pl .. 1/?
    #   Failed test 'check for unhandled atomic updates: bug_29596.pl'
    #   at ./t/00-check-atomic-updates.pl line 34.
    #                   'bug_29596.pl'
    #           matches '(?^u:.*pl$)'
    # Looks like you failed 1 test of 3.
    ./t/00-check-atomic-updates.pl .. Dubious, test returned 1 (wstat 256, 0x100)
    Failed 1/3 subtests

JD Amended patch: fix copyright year
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>