Bug 15432: t/db_dependent/Letters.t depends on external data/configuration

To test:

- Set system preference LetterLog to 'Don't log'
- prove t/db_dependent/Letters.t
- Result: Fails on test 62 - Successfully sent claim
- Apply patch
- Test again
- Result: Pass OK

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Amended patch: removed the bug reference, not needed.

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit c92b1556ef)
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
(cherry picked from commit 99fc3af0a6)
Signed-off-by: Frédéric Demians <f.demians@tamil.fr>

t/db_dependent/Letters.t

@@ -354,6 +354,9 @@ $bookseller->contacts->[0]->email('testemail@mydomain.com');
 C4::Bookseller::ModBookseller($bookseller);
 $bookseller = Koha::Acquisition::Bookseller->fetch({ id => $booksellerid });
 
+# Ensure that the preference 'LetterLog' is set to logging
+C4::Context->set_preference( 'LetterLog', 'on' );
+
 warning_is {
     $err = SendAlerts( 'claimacquisition', [ $ordernumber ], 'TESTACQCLAIM' ) }
     "Fake sendmail",