LP 1333893: Keep Empty Bib on Volume Transfer

LP 1333893: Keep Empty Bib on Volume Transfer

Volume transfer did not honor the cat.bib_keep_on_empty organizational
unit setting when removing empty bib records.  This commit changes it
so that it does in the same manner that deleting copies and volumes
does.

To test this fix, set cat.bib_keep_on_empty for your workstation
org. unit to true, and then transfer all of the volumes from one bib
record to another.  The empty bib record should not get deleted.

You can also test with the setting on false to make sure that the
empty bib gets deleted.

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