Bug 20286: Correctly escape URI characters in OPAC RSS template

Bug 20286: Correctly escape URI characters in OPAC RSS template

Bug 19568 use the TT filter url whereas it must have escaped the URI
characters with the uri filter.

Test plan:
Subscribe to an OPAC search
=> Without this patch you will get an empty page
=> With this patch applied you will see result list.

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Brendan Gallagher <brendan@bywatersolutions.com>
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>