Bug 27979: Modify TrackClicks to verify URL exists in DB when multiple uri

Bug 27979: Modify TrackClicks to verify URL exists in DB when multiple uri

To test:
1) Go to Admin -> system preferences and enable the TrackClicks syspref
(set to Track or Track anonymously)
2) Find a record in the staff client with an item. Edit the item and put
two external URLs in the Uniform Resource Identifier field, e.g.
"https://www.google.com/ | https://twitter.com/"
3) Search for that record in the OPAC. Notice the two links in the
holdings table.
4) Click a link and confirm that you are directed to a 404.
5) Apply the patch and refresh the page
6) Click a link and confirm that you are directed to the page as
expected
7) Go back to edit the record in the staff client and remove one of the
links from the URI field
8) Go back to the OPAC and confirm you can still access the link as
expected when there is only one URI

Sponsored-by: Catalyst IT
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>