Update git submodules

* Update docs/submodules/openretriever from branch 'master'
  - Add k8s installation by vagrant + kubeadm

    Change-Id: I4d858e1d0d6779f9f78c0a74ee032ef92d8a4eb8
    Signed-off-by: Guo Ruijing <ruijing.guo@intel.com>

diff --git a/docs/submodules/openretriever b/docs/submodules/openretriever
index aaec204..ddaccb3 160000 (submodule)
--- a/docs/submodules/openretriever
+++ b/docs/submodules/openretriever
@@ -1 +1 @@
-Subproject commit aaec204c4ac47a8980b8db5e6d55d169f78204f7
+Subproject commit ddaccb38f85dba6bec1fcd79b0b4cce45d92192e