Bug 20218: Fix matching of uri in tracklinks

Bug 20218: Fix matching of uri in tracklinks

The current code matches using a regex, this breaks when the url
contains special characters. We swtich it to equality check

To test:
1 - Enable TrackClicks (either track or anonymous)
2 - Find the URL of a biblio in the OPAC
3 - Paste this into the 856$u of another record
    (or use any url containing a '?' or other characters)
4 - View the record in the opac
5 - Click the URL
6 - 404 Error!
7 - Apply patch
8 - Try again
9 - Success!

Signed-off-by: Claire Gravely <claire.gravely@bsz-bw.de>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>