Update git submodules

* Update docs/submodules/sdnvpn from branch 'stable/danube'
  - Fix failure in router association- testcase8

    Due to some latency at the creation of the instance 8-1
    somitimes the router association between  'sdnvpn-8-1-router' and net 'sdnvpn-8-2'
    fails.

    The case could be more robust, increasing the number of ping tries from
    its current value (=1)

    JIRA: SDNVPN-102

    Change-Id: I3b9701c40f1221cfebc540d312b61bb881389762
    Signed-off-by: tomsou <soth@intracom-telecom.com>
    (cherry picked from commit 5d93773cd66119ac49d9feb171b5fc9108e53fca)

diff --git a/docs/submodules/sdnvpn b/docs/submodules/sdnvpn
index ce12119..3d5118b 160000 (submodule)
--- a/docs/submodules/sdnvpn
+++ b/docs/submodules/sdnvpn
@@ -1 +1 @@
-Subproject commit ce12119b306d0269bf9710e9a48b5ef5c3134f6c
+Subproject commit 3d5118b75dbf13b81aa84b3434d4db91e229a8ac