LP#1848975 - open-ils.search.biblio.record.mods_slim.retrieve Array warning

LP#1848975 - open-ils.search.biblio.record.mods_slim.retrieve Array warning

When calling open-ils.search.biblio.record.mods_slim.retrieve with an
array of record ids, there is a warning because the wrong comparison
operator is used.  Using eq instead of == fixes the warning.

Testing can be done with srfsh and a command like

srfsh# request open-ils.search open-ils.search.biblio.record.mods_slim.retrieve [102916]

Check the logs for the warning, and then lack of warning.

Signed-off-by: Josh Stompro <stompro@stompro.org>