Allow to reuse connections that wait their first request.

This should improve behavior under deficiency of connections.

Since SSL handshake usually takes significant amount of time,
we exclude connections from reusable queue during this period
to avoid premature flush of them.

src/http/ngx_http_request.c

diff --git a/src/http/ngx_http_request.c b/src/http/ngx_http_request.c
index 87df262..1cab9ee 100644
--- a/src/http/ngx_http_request.c
+++ b/src/http/ngx_http_request.c
@@ -355,6 +355,7 @@
     }
 
     ngx_add_timer(rev, c->listening->post_accept_timeout);
+    ngx_reusable_connection(c, 1);
 
     if (ngx_handle_read_event(rev, 0) != NGX_OK) {
         ngx_http_close_connection(c);
@@ -383,6 +384,11 @@
         return;
     }
 
+    if (c->close) {
+        ngx_http_close_connection(c);
+        return;
+    }
+
     hc = c->data;
     cscf = ngx_http_get_module_srv_conf(hc->conf_ctx, ngx_http_core_module);
 
@@ -432,6 +438,7 @@
 
         if (!rev->timer_set) {
             ngx_add_timer(rev, c->listening->post_accept_timeout);
+            ngx_reusable_connection(c, 1);
         }
 
         if (ngx_handle_read_event(rev, 0) != NGX_OK) {
@@ -466,6 +473,8 @@
 
     c->log->action = "reading client request line";
 
+    ngx_reusable_connection(c, 0);
+
     c->data = ngx_http_create_request(c);
     if (c->data == NULL) {
         ngx_http_close_connection(c);
@@ -611,6 +620,11 @@
         return;
     }
 
+    if (c->close) {
+        ngx_http_close_connection(c);
+        return;
+    }
+
     n = recv(c->fd, (char *) buf, 1, MSG_PEEK);
 
     err = ngx_socket_errno;
@@ -631,6 +645,7 @@
 
             if (!rev->timer_set) {
                 ngx_add_timer(rev, c->listening->post_accept_timeout);
+                ngx_reusable_connection(c, 1);
             }
 
             if (ngx_handle_read_event(rev, 0) != NGX_OK) {
@@ -670,6 +685,8 @@
                     ngx_add_timer(rev, c->listening->post_accept_timeout);
                 }
 
+                ngx_reusable_connection(c, 0);
+
                 c->ssl->handler = ngx_http_ssl_handshake_handler;
                 return;
             }
@@ -714,6 +731,8 @@
         c->read->handler = ngx_http_wait_request_handler;
         /* STUB: epoll edge */ c->write->handler = ngx_http_empty_handler;
 
+        ngx_reusable_connection(c, 1);
+
         ngx_http_wait_request_handler(c->read);
 
         return;