Update git submodules

* Update docs/submodules/sdnvpn from branch 'stable/danube'
  - Add Labels

    Labels serve as refs when referenced
    from other documents.

    Change-Id: I37b93bae1283d2ea8638fc49c0c40fe7badf61ad
    Signed-off-by: ShubhamRathi <shubhamiiitbackup@gmail.com>
    (cherry picked from commit d900e3f166536bfffdfba094757fbee4337630b8)

diff --git a/docs/submodules/sdnvpn b/docs/submodules/sdnvpn
index 2648675..3be7276 160000 (submodule)
--- a/docs/submodules/sdnvpn
+++ b/docs/submodules/sdnvpn
@@ -1 +1 @@
-Subproject commit 2648675ac9e71f3de44c3a0c26135cdeec5c97d1
+Subproject commit 3be72766b6686072d1014a4b3bac56c373a5ed6a