Bug 22478: (QA follow-up) Handle category in opac-shelves like a boolean

Bug 22478: (QA follow-up) Handle category in opac-shelves like a boolean

The category parameter should be restricted to 1 or 2 (private/public). In
order to keep same behavior, no parameter means 1 (private).
Note: Adding the same line in intranet counterpart.

Test plan
[1] Check for category empty, '1a', '11' etc. And with script ;)

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>