dashboard: sync from apisix_dashboard.

fixed https://github.com/iresty/apisix/issues/388
diff --git a/dashboard b/dashboard
index e98df93..82bc79e 160000
--- a/dashboard
+++ b/dashboard
@@ -1 +1 @@
-Subproject commit e98df93152d2248f9fa6192dd07cf6b25fe82c05
+Subproject commit 82bc79e583a852be552acfd02b3e794e884e6077