Handle Missing copy status (4) in checkin_via_barcode2 in circ.util.js.

We treate just like available and reshelving.

Signed-off-by: Jason Stephenson <jstephenson@mvlc.org>
Signed-off-by: Kathy Lussier <klussier@masslnc.org>
Signed-off-by: Dan Wells <dbw2@calvin.edu>