Update git submodules

* Update docs/submodules/sdnvpn from branch 'master'
  - Merge "Update Overview document for Gambia release"
  - Update Overview document for Gambia release

    JIRA: SDNVPN-224

    Change-Id: Id02780698fc84f750c6d633fbcf0b86a04c13d32
    Signed-off-by: dimitris.tsiolakis <dmts@intracom-telecom.com>

diff --git a/docs/submodules/sdnvpn b/docs/submodules/sdnvpn
index 999551a..8641815 160000 (submodule)
--- a/docs/submodules/sdnvpn
+++ b/docs/submodules/sdnvpn
@@ -1 +1 @@
-Subproject commit 999551a559ec9ab27a9e8f355b5801dbc93a8677
+Subproject commit 8641815e160a5b339467f3d39fe7d21f4ab08212