Upstream: don't keep connections on early responses (ticket #669).

src/http/modules/ngx_http_upstream_keepalive_module.c

diff --git a/src/http/modules/ngx_http_upstream_keepalive_module.c b/src/http/modules/ngx_http_upstream_keepalive_module.c
index 51887b4..85bfcdb 100644
--- a/src/http/modules/ngx_http_upstream_keepalive_module.c
+++ b/src/http/modules/ngx_http_upstream_keepalive_module.c
@@ -302,6 +302,10 @@
         goto invalid;
     }
 
+    if (!u->request_body_sent) {
+        goto invalid;
+    }
+
     if (ngx_terminate || ngx_exiting) {
         goto invalid;
     }

src/http/ngx_http_upstream.c

diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index 6c6ee80..99ef3ae 100644
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -1441,6 +1441,7 @@
     }
 
     u->request_sent = 0;
+    u->request_body_sent = 0;
 
     if (rc == NGX_AGAIN) {
         ngx_add_timer(c->write, u->conf->connect_timeout);
@@ -1825,6 +1826,8 @@
 
     /* rc == NGX_OK */
 
+    u->request_body_sent = 1;
+
     if (c->write->timer_set) {
         ngx_del_timer(c->write);
     }

src/http/ngx_http_upstream.h

diff --git a/src/http/ngx_http_upstream.h b/src/http/ngx_http_upstream.h
index 8404265..4246c8a 100644
--- a/src/http/ngx_http_upstream.h
+++ b/src/http/ngx_http_upstream.h
@@ -370,6 +370,7 @@
     unsigned                         upgrade:1;
 
     unsigned                         request_sent:1;
+    unsigned                         request_body_sent:1;
     unsigned                         header_sent:1;
 };