Update git submodules

* Update docs/submodules/sdnvpn from branch 'master'
  - Fix the wrong image path for base image

    The images are put under new directory while the code is still using
    old path

    Change-Id: I6dfa59ffe6bde316f155560449979bd10354b43c
    Signed-off-by: helenyao <yaohelan@huawei.com>

diff --git a/docs/submodules/sdnvpn b/docs/submodules/sdnvpn
index 510ce10..f27dee4 160000 (submodule)
--- a/docs/submodules/sdnvpn
+++ b/docs/submodules/sdnvpn
@@ -1 +1 @@
-Subproject commit 510ce10d0c31251a565af9c554918aeccf871382
+Subproject commit f27dee492379404be1570c37a2c76bdbe234abc4