Bug 26639: Add auto_savepoint to DBIC connection

Bug 26639: Add auto_savepoint to DBIC connection

See comment 0.

https://metacpan.org/pod/distribution/DBIx-Class/lib/DBIx/Class/Manual/Cookbook.pod#Nested-transactions-and-auto-savepoints

Otherwise:
DBIx::Class::Storage::txn_rollback(): A txn_rollback in nested transaction is ineffective! (depth 1) at t/db_dependent/Koha/Objects.t line 274

Possible side-effects? Slowness?

We need to push it to master ASAP and see how our test suite behave.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>