Bug 18977: Rollback branch in t/db_dependent/SIP/Message.t

Bug 18977: Rollback branch in t/db_dependent/SIP/Message.t

To test:
1. Before applying patch, check the amount of branches in database
2. prove t/db_dependent/SIP/Message.t
3. See that a new branch is stored
4. Apply patch
5. prove t/db_dependent/SIP/Message.t
6. See that a new branch is no longer stored

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit 139b66f65611cff0a2551662e0fd5c2e50b4c10f)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>