Bug 21865: ES compatiblity of remove_unused_authorities.pl

Bug 21865: ES compatiblity of remove_unused_authorities.pl

The script misc/migration_tools/remove_unused_authorities.pl directly checks if Zebra search is OK.

This patch changes so that this test is only if Zebra is the search engine.
It also adds a test on the search off any authority number indexed (index 'an').
With Zebra its : an,alwaysmatches=''
With ES its : an:*
This test ensure that biblios records are indexed and that not all autorities will be deleted.

Test plan:
1) On a catalog create a new authority
2) Use Zebra in systempreference SearchEngine
3) Stop Zebra server
4) Run misc/migration_tools/remove_unused_authorities.pl -c
5) The script does nothing and says :
   Zebra server seems not to be available. This script needs Zebra runs.
6) Restart Zebra server
7) Delete biblio index base
8) Run misc/migration_tools/remove_unused_authorities.pl -c
9) The script does nothing and says :
   Searching authority number in biblio records seems not to be available : an,alwaysmatches=''
10) Use ElasticSearch in systempreference SearchEngine
11) Delete biblio index base
12) Run misc/migration_tools/remove_unused_authorities.pl -c
13) The script does nothing and says :
    Searching authority number in biblio records seems not to be available : an:*

Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>