Bug 25701: (bug 14419 follow-up) Always display facet groups in the same order

Bug 25701: (bug 14419 follow-up) Always display facet groups in the same order

It seems that this regression comes from bug 14419, but I have not found
a logic reason behind that.
This patch restores the behaviour we always had: facet groups must be
displayed in a given order: the Zebra index (au, ccode, holdingbranch,
etc.)

Test plan:
Apply this patch, restart all and confirm that the facets are not moving
up and down when you refresh your search result page.

QA note:
I think the following line must be removed
@facets_loop = sort {defined $a->{expand} && defined $b->{expand} && $a->{expand} cmp $b->{expand}} @facets_loop;

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>