Actually close the Server's underlying SocketServer
Actually close the Server's underlying SocketServer

This is mentioned in the Python 2 documentation for SocketServer, but
not Python 3. As it happens, the default SocketServer doesn't do
anythign when this is called, so omitting to call it does not harm, but
we do want to ensure that our thread pool is closed when exiting.

yrro/temper-exporter,yrro/temper-exporter