When a user views holds in their account, clicking "only available"

When a user views holds in their account, clicking "only available"
on the holds screen or "Ready for Pickup" in the navbar will add an
"available=1" parameter. However, if the user then attempts to return
to a list of all holds, the "available" parameter is not cleared, and
the user will only see holds available for pickup.

This commit will clear those parameters.

Signed-off-by: Kathy Lussier <kmlussier@masslnc.org>
Signed-off-by: Ben Shum <bshum@biblio.org>
Signed-off-by: Bill Erickson <berick@esilibrary.com>