Bug 10452: (follow-up) remove duplicate check of damaged status

Bug 10452: (follow-up) remove duplicate check of damaged status

While reviewing the main patch for this bug to verify that the
holds queue routines and C4::Reserves had the same conception of
when a damaged item could fill a hold request, I noticed that
GetItemsAvailableToFillHoldRequestsForBib() duplicated the code
for adding an SQL clause to filter out damaged items.  This patch
removes the duplication and improves the POD for that routine.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>