Update git submodules

* Update docs/submodules/sdnvpn from branch 'master'
  - Merge "Updating docs for Euphrates"
  - Updating docs for Euphrates

    Moved previous user guide content into the right places,
    updating the section structure along the way.

    Started to edit the release notes but this needs more work.
    This will be merged now to enable link checking by the docs team.
    Remaining chan ges to be done in a separate review.

    JIRA: SDNVPN-185

    Change-Id: Idd128b05f8ceb7195086b813d499b3f12243d025
    Signed-off-by: Tim Irnich <tim.irnich@ericsson.com>

diff --git a/docs/submodules/sdnvpn b/docs/submodules/sdnvpn
index 236b16b..778d487 160000 (submodule)
--- a/docs/submodules/sdnvpn
+++ b/docs/submodules/sdnvpn
@@ -1 +1 @@
-Subproject commit 236b16b97ace3a7fc8bd6719a034443e076dc039
+Subproject commit 778d4874047341c2b6af5c91c7553cc15e1cdaaf