Update git submodules

* Update docs/submodules/ovno from branch 'stable/euphrates'
  - Updated doc structure and added index file

    Created userguide/ under release/ and added an index.rst to enable
    document rendering.

    Change-Id: I868b4f5d4834b28b3fd184550a13f087cbe19b1c
    Signed-off-by: Sofia Wallin <sofia.wallin@ericsson.com>
    (cherry picked from commit 8b0f080fafe6fd3e150cb669f8087ec1c2b9be23)

diff --git a/docs/submodules/ovno b/docs/submodules/ovno
index fd876b7..6d1c549 160000 (submodule)
--- a/docs/submodules/ovno
+++ b/docs/submodules/ovno
@@ -1 +1 @@
-Subproject commit fd876b7dbc7d517a706b22e52bf6f0e8f79a0b4b
+Subproject commit 6d1c5491ffc6dd72c6a93083a5aaba29378e9a72