Upstream: handling of upstream SSL handshake timeouts.

Previously SSL handshake timeouts were not properly logged, and resulted
in 502 errors instead of 504 (ticket #1126).

src/http/ngx_http_upstream.c

diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index a6dd55e..ed25f43 100644
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -1666,6 +1666,13 @@
         return;
     }
 
+    if (c->write->timedout) {
+        c = r->connection;
+        ngx_http_upstream_next(r, u, NGX_HTTP_UPSTREAM_FT_TIMEOUT);
+        ngx_http_run_posted_requests(c);
+        return;
+    }
+
 failed:
 
     c = r->connection;