connection error should be logged with "connecting to upstream" action,
the bug was introduced in r1154

src/http/ngx_http_upstream.c

diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index 650c84c..ae5f3d3 100644
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -1290,6 +1290,7 @@
 
     if (ngx_event_flags & NGX_USE_KQUEUE_EVENT)  {
         if (c->write->pending_eof) {
+            c->log->action = "connecting to upstream";
             (void) ngx_connection_error(c, c->write->kq_errno,
                                     "kevent() reported that connect() failed");
             return NGX_ERROR;
@@ -1313,6 +1314,7 @@
         }
 
         if (err) {
+            c->log->action = "connecting to upstream";
             (void) ngx_connection_error(c, err, "connect() failed");
             return NGX_ERROR;
         }