SSL: disabled sending shutdown after ngx_http_test_reading(). Sending shutdown when ngx_http_test_reading() detects the connection is closed can result in "SSL_shutdown() failed (SSL: ... bad write retry)" critical log messages if there are blocked writes. Fix is to avoid sending shutdown via the c->ssl->no_send_shutdown flag, similarly to how it is done in ngx_http_keepalive_handler() for kqueue when pending EOF is detected. Reported by Jan Prachař (http://mailman.nginx.org/pipermail/nginx-devel/2018-December/011702.html).