Update git submodules

* Update docs/submodules/sdnvpn from branch 'master'
  - Merge "Local Documentation Builds"
  - Local Documentation Builds

        This adds configuration for performing local documentation builds
        with the following simple command:

        tox -e docs

    added index.rst so that docs build succsesfully

    Change-Id: Ib0c7626c37b7f733641fcf2174d9951bf2371886
    Signed-off-by: Aric Gardner <agardner@linuxfoundation.org>

diff --git a/docs/submodules/sdnvpn b/docs/submodules/sdnvpn
index 4d98432..7b1b9e2 160000 (submodule)
--- a/docs/submodules/sdnvpn
+++ b/docs/submodules/sdnvpn
@@ -1 +1 @@
-Subproject commit 4d9843200ef1dde2442667cd077afb24f09087ba
+Subproject commit 7b1b9e2ff57ceb2a75b3d60b95262c12e1823586