LP 1904737: Expand Hold Targeter Current Copy Statuses

LP 1904737: Expand Hold Targeter Current Copy Statuses

The open-ils.hold-targeter service would previously limit the current
copy for a hold to those copies with a status of 0 or 7.  This commit
changes this behavior to retrieve the copy statuses that have the
holdable and is_available fields both set to true.  This is required
for such copies to appear on the holds pull list.

In order to limit the number of queries to retrieve the list of copy
statuses, an app_setting is added to the open-ils.hold-targeter
configuration in the opensrf.xml file, status_cache_time.  This field
can be set to the number of seconds that a hold targeter drone should
wait before checking for changes to the copy statuses in the database.
If you don't make changes or additions to the copy statuses very
often, this should be a large number.  If the setting is missing or
set to zero, then a default value of 300 (5 minutes) is used.

Signed-off-by: Jason Stephenson <jason@sigio.com>