Update git submodules

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

    JIRA: SDNVPN-225

    Change-Id: Ibc883d5e38ae88538735d52a114b65dda86770b9
    Signed-off-by: dimitris.tsiolakis <dmts@intracom-telecom.com>

diff --git a/docs/submodules/sdnvpn b/docs/submodules/sdnvpn
index bdec0f1..999551a 160000 (submodule)
--- a/docs/submodules/sdnvpn
+++ b/docs/submodules/sdnvpn
@@ -1 +1 @@
-Subproject commit bdec0f1283bc91a4c78b858a28d25f76a0413cd2
+Subproject commit 999551a559ec9ab27a9e8f355b5801dbc93a8677