LP#1339190: support disconnection for SIP multiplex purposes

This patch adds a disconnect method to close the OpenSRF
connect; this method is invoked only when the Net::Server::Multiplex
personality is in use.

Signed-off-by: Mike Rylander <mrylander@gmail.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>
LP#1339190: Have Evergreen save authtoken state to support IO::Multiplex mode

Signed-off-by: Mike Rylander <mrylander@gmail.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>