Bug 28139: Simplify logic for handling found holds in returns.pl

Bug 28139: Simplify logic for handling found holds in returns.pl

We are handling in this if-else block 3 cases:
 - Hold found and waiting
 - Hold found but not waiting AND whether HoldsAutoFill is enabled
 - Hold found but not waiting AND whether HoldsAutoFill disabled

If we simply first handle hold found = Waiting case first then we
don't have to individually list all those other found cases and that
simplifies this code a lot.

To test:
 1. Apply patch
 2. Make sure HoldsAutoFill is disabled
 3. Make item-level hold on branch A
 4. Check-in the item at branch A and you should get pop-up confirming
    the hold, ignore it
 5. Set HoldsAutoFill is enabled
 4. Check-in the item again and you now the hold should have been
    automatically filled

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>