Update git submodules

* Update docs/submodules/sdnvpn from branch 'master'
  - Merge "Inheritance from Feature class"
  - Inheritance from Feature class

    Change-Id: I81aa9582452ca43a4eab32ba34a640043c89043e
    Signed-off-by: Jose Lausuch <jalausuch@suse.com>

diff --git a/docs/submodules/sdnvpn b/docs/submodules/sdnvpn
index cd6a598..6f4fa99 160000 (submodule)
--- a/docs/submodules/sdnvpn
+++ b/docs/submodules/sdnvpn
@@ -1 +1 @@
-Subproject commit cd6a598f8e0c18820783d0b0e9d3135fa833d826
+Subproject commit 6f4fa990aec1d58d39930311640cd6f086e5b696