LP#1269042: prevent acq seach from building dropdown of every copy ID in the DB

This patch ensures that if a user sets a search field in the
acquisitions general search form to the line item details copy ID
(labeled "LID - Evergreen Copy ID"), the form presents a normal
input widget rather than trying to build a drop-down containing
every copy ID in the database.  Except for very small databases,
the previous behavior would mean that an open-ils.pcrud backend
would eventually consume a great deal of memory trying to service
a request for all copies in the system.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Mike Rylander <mrylander@gmail.com>