Bug 28573: Replace authority record with Z39.50/SRU creates new authority record

Bug 28573: Replace authority record with Z39.50/SRU creates new authority record

When trying to replace an authority record with Z39.50/SRU then a new authority
record is created without deleting the old one and not link the new one with
any record.

This patch fixes that.

Test plan:

1) Try to catalogue a new authority record from cataloguing form.
2) Try to replace that authority record with Z39.50/SRU, then a new authority
record is created and also you have that one that you tried to replace.
3) Apply the patch.
4) Try to replace the authority from step1 with Z39.50/SRU, then is working as
expected.

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>
Signed-off-by: Eric Phetteplace <phette23@gmail.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>