Bug 21759: Avoid manually setting amountoutstanding in _FixAccountForLostAndReturned

Bug 21759: Avoid manually setting amountoutstanding in _FixAccountForLostAndReturned

This patch changes the behaviour in the _FixAccountForLostAndFound
method.

The method will now add the amountoutstanding value for the lost item
fee to the CR credit to be generated. This means that:
- If there's some remaining debt, the same amount  will be added to the
  CR credit and used to cancel that debt. The final amountoutstanding
  will be the same as before, but an offset will be generated as
  required.
- If the line was written off, the behaviour remains unchanged, so no
  offset.
- If the line was payed and/or written off in full only the payments are
  refund, preserving the current behaviour.

To test:
- Apply the regression tests patch
- Run:
  $ kshell
 k$ prove t/db_dependent/Circulation.t
=> FAIL: Tests fail because the behaviour is not correct
- Apply this patch
- Run:
 k$ prove t/db_dependent/Circulation.t
=> SUCCESS: Tests now pass!
- Sign off :-D

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>