We modify NCIP::ILS::Evergreen->find_location_failover to return an
undefined value in the event of failure to lookup an agency.
We then modify the requestitem and cancelrequestitem handlers to
return a Problem message if the lookup fails for their selection
org. units. These appear to be the only two places possilby
affected by a failure to find a location.
Signed-off-by: Jason Stephenson <jstephenson@mvlc.org>