Update git submodules

* Update docs/submodules/sdnvpn from branch 'master'
  - Merge "Wait for instance deletion"
  - Wait for instance deletion

    JIRA: SDNVPN-222

    Confirm the deletion of instance in order to prevent its port
    existence when trying to delete relevant subnet in a later stage.

    Change-Id: Iace0fbbd90d50f05764ac09682caae59baba22fa
    Signed-off-by: Stamatis Katsaounis <mokats@intracom-telecom.com>

diff --git a/docs/submodules/sdnvpn b/docs/submodules/sdnvpn
index 785fed1..e97d0c5 160000 (submodule)
--- a/docs/submodules/sdnvpn
+++ b/docs/submodules/sdnvpn
@@ -1 +1 @@
-Subproject commit 785fed155091a3eeca81dd07c2d308145ef2d98d
+Subproject commit e97d0c53a5b15e590e03ba86972eed26db4009c0