Bug 25429: (QA follow-up) Add extra variable for days

Bug 25429: (QA follow-up) Add extra variable for days

I think it is a bit more clear to use another variable for the
number of days from the preferences than overwriting the flag
variable.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Tested by adding an authval for LOST.
Filling prefs ClaimReturnedLostValue, CleanUpDatabaseReturnClaims.
Claiming a return, resolving it. Setting date back via SQL.
Running the script with -v --return-claims, toggling --confirm.
The claim is counted and deleted with confirm.

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>