Bug 16143: Make opac-shelves.pl generate OPAC itype images path

 Bug 16143: Make opac-shelves.pl generate OPAC itype images path

This patch makes icons point to the OPAC path instead of intranet's.

To test:
- On current master/3.22.x
- Have some itemtypes with icons set
- Have some biblios matching the itemtypes
- Add them to a public list
- Do a search in the OPAC for any of those biblios
=> SUCCESS: icons show correctly
- Choose the list
=> FAIL: icons fail to show, URL points to /intranet-tmpl/....
- Apply the patch, reload
=> SUCCESS: icons show correctly
- Sign off :-D

Sponsored-by: American Numismatic Society
NOTE: I had to set item-level_itypes to 'biblio record'
      in order to trigger this. My icon's showed, but the
      path was wrong. This patch corrects it.

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Brendan A Gallagher <brendan@bywatersolutions.com>