Bug 11652: ensure that merging authority records corrects biblios

Bug 11652: ensure that merging authority records corrects biblios

When merging authority records in librarian interface biblio records
linked to deleted authority are not being corrected (i.e. have still
old heading and orpaned link in $9).

Test plan:
1. Have two authorities in the catalogue, linked to biblio records.
2. Merge them with the new merge facility (cf. Bug 5202).
3. Have a look a the biblio record(s) previously linked to the removed
   authority. It should still have the old heading AND orpaned authority
   link in $9.

4. Apply the patch.
5. Refresh the test records (or use another set).
6. Repeat 1-3. Headings should be refreshed and the correct authid link
   should be in $9 now.

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Passes all tests and QA script.
Note: new record count on the authority record will show
      after reindexing.
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit 0070a7f6afb30b6f7ae8bc0eb073a4c39e0f783a)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>