Bug 10299: authority plugin - authority field are reversed

Bug 10299: authority plugin - authority field are reversed

If you click the plugin next to an authority field that is already
populated it takes the values from the field and puts them in the search
in the reverse order.

Test plan:
1/ Edit a biblio
2/ Fill the subfield for an authority field (for instance 650$v, 650$x,
650$y, etc.)
3/ Click on the authority plugin
Before this patch, the values were concatenated in the reverse order.
With this patch, it should not.

Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
Work as described, no koha-qa errors

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>