Update git submodules

* Update docs/submodules/sdnvpn from branch 'stable/danube'
  - Removing peering testcase for Apex

    Change-Id: Ifad3f84fcb0c5dfa07aca43d74a027e3522abb87
    Signed-off-by: Nikolas Hermanns <nikolas.hermanns@ericsson.com>
    (cherry picked from commit c0080201984842b64b91ea3cb0fc96ca03fe303c)

diff --git a/docs/submodules/sdnvpn b/docs/submodules/sdnvpn
index 9b058c2..2b4934d 160000 (submodule)
--- a/docs/submodules/sdnvpn
+++ b/docs/submodules/sdnvpn
@@ -1 +1 @@
-Subproject commit 9b058c2eba119369d847a383ae7c0656273ee284
+Subproject commit 2b4934d59544b307e8847cb77ff6948c8ba67f7d