Update git submodules

* Update docs/submodules/sdnvpn from branch 'master'
  - Switch from CONST to CONF

    CONST is not the right Functest object to get config data.

    Change-Id: I764a0a2a24447c941d1e726f3116593b29dd1c1e
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/sdnvpn b/docs/submodules/sdnvpn
index 45194ef..4e6758b 160000 (submodule)
--- a/docs/submodules/sdnvpn
+++ b/docs/submodules/sdnvpn
@@ -1 +1 @@
-Subproject commit 45194eff156234cea416b94d7988a1ccf8a891e6
+Subproject commit 4e6758bb8d2501b7e050910f9351223976b20101