LP#1248636: Clear session at OPAC logout

When the user explicitly logs out, clear the session on the server side.

Signed-off-by: Mike Rylander <mrylander@gmail.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Ben Shum <bshum@biblio.org>
Forward port 2.7.0-2.7.1 upgrade script

Signed-off-by: Ben Shum <bshum@biblio.org>