Fixed worker_shutdown_timeout in various cases.

Fixed worker_shutdown_timeout in various cases.

The ngx_http_upstream_process_upgraded() did not handle c->close request,
and upgraded connections do not use the write filter.  As a result,
worker_shutdown_timeout did not affect upgraded connections (ticket #1419).
Fix is to handle c->close in the ngx_http_request_handler() function, thus
covering most of the possible cases in http handling.

Additionally, mail proxying did not handle neither c->close nor c->error,
and thus worker_shutdown_timeout did not work for mail connections.  Fix is
to add c->close handling to ngx_mail_proxy_handler().

Also, added explicit handling of c->close to stream proxy,
ngx_stream_proxy_process_connection().  This improves worker_shutdown_timeout
handling in stream, it will no longer wait for some data being transferred
in a connection before closing it, and will also provide appropriate
logging at the "info" level.