BUG/MINOR: http: log 407 in case of proxy auth

Commit 844a7e7 ("[MEDIUM] http: add support for proxy authentication")
merged in v1.4-rc1 added the ability to emit a status code 407 in auth
responses, but forgot to set the same status in the logs, which still
contain 401.

The bug is harmless, no backport is needed.
diff --git a/src/proto_http.c b/src/proto_http.c
index 27693ac..6f6bb0d 100644
--- a/src/proto_http.c
+++ b/src/proto_http.c
@@ -3953,7 +3953,7 @@
 			realm = (objt_applet(s->target) == &http_stats_applet) ? STATS_DEFAULT_REALM : px->id;
 
 		chunk_printf(&trash, (txn->flags & TX_USE_PX_CONN) ? HTTP_407_fmt : HTTP_401_fmt, realm);
-		txn->status = 401;
+		txn->status = (txn->flags & TX_USE_PX_CONN) ? 407 : 401;
 		stream_int_retnclose(req->prod, &trash);
 		/* on 401 we still count one error, because normal browsing
 		 * won't significantly increase the counter but brute force