Bug 18131: ES - Fix matching staged records

Bug 18131: ES - Fix matching staged records

The code in C4::Matches::get_matches is terrible and a bug has been introduced
by bug 12478 because of its way to handle uniqueness.

If search engine is elastic, simple_search_compat returns array ref of MARC::Record,
used as a string for the key of the matches hashref we get things like
"MARC::Record=HASH(0x8f76ab0)".
Yes, terrible...

The file is never staged and we get an internal server error:
    stage-marc-import.pl: Can't locate object method "fields" via package "MARC::Record=HASH(0x8f76ab0)" (perhaps you forgot to load "MARC::Record=HASH(0x8f76ab0)"?) at /home/vagrant/kohaclone/C4/Biblio.pm line 2691

To recreate the issue:
- Set SearchEngine == Elastic
- Create a matching rule on 999$c (you need to edit the existing one and specify
'Local-number' as search index, not 'local-number')
- Import a file with bibliographic records and use the matching rule you defined.

Test plan:
Import authority and bibliographic records with Zebra and Elastic using a matching rule.
Everything should work correctly.

Note: I found a bug when importing authorities using Elastic, see bug 17255 comment 38.

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>