Changed bib merge to ignore deleted call numbers.

The asset.merge_record_assets function was not checking for deleted call numbers
and merging items onto deleted call numbers that of course causes issues.

Signed-off-by: Steve Callender <stevecallender@esilibrary.com>
Signed-off-by: Ben Shum <bshum@biblio.org>
Stamping upgrade script for Bib Merge Ignore Deleted Call Numbers

Signed-off-by: Ben Shum <bshum@biblio.org>