Further fixes for hold-driven recalls

Further fixes for hold-driven recalls

Force a scalar context on the array reference of circs returned
from the search clause to short-circuit the recall processing
if we have no applicable circs to work through.

Also, open-ils.trigger.event.autocreate needs a Fieldmapper object,
not a raw CDBI object, so invoke the to_fieldmapper() method to
convert it accordingly (thanks to miker for the assist!)

git-svn-id: svn://svn.open-ils.org/ILS/trunk@18837 dcc99617-32d9-48b4-a31d-7c20da2025e4