CanBookBeReserved uses the very heavy-weight function GetItemsInfo to simply retrieve
the itemnumbers attached to a given biblio. The function get_itemnumbers_of() is much
lighter-weight and returns the required information; switching to it will reduce the overall
system resource cost of placing a hold.
Signed-off-by: Nicole C. Engard <nengard@bywatersolutions.com> Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>