Fix for Bug 5898 - search to hold feature not clearing

Fix for Bug 5898 - search to hold feature not clearing

Search to hold cookie is now cleared when the user loads a blank
circulation page and when the user logs out.

The user also now has the option to "forget" the current
search to hold patron by choosing an option from the
search to hold menu on the search results page.

Signed-off-by: Liz Rea <lrea@nekls.org>
Tested:
Forget <patron> from search to hold results clears cookie
Logging out clears the cookie - testing note: i had to clear my cookies and test fresh before this would work
Loading a blank circulation page (Check Out from the circulation-home) clears the cookie.

Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>
Signed-off-by: Ian Walls <ian.walls@bywatersolutions.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>