Update git submodules

* Update docs/submodules/sdnvpn from branch 'stable/fraser'
  - potential fix for attaching router with external network gateway

    In the CI environment, whenever testcases attaches a router with
    external network gateway sometimes it throws the error "No more IP
    addresses available on network". This could be due to stale floating
    ip's exist in the deployment which is cleaned up now before executing
    sdnvpn testsuite.

    JIRA: SDNVPN-212

    Change-Id: I027a833f13b1bdddd83dc8c7e7f7292e20b10bb8
    Signed-off-by: Periyasamy Palanisamy <periyasamy.palanisamy@ericsson.com>
    (cherry picked from commit 1bf65fd6d92cdf2c0ad694662cbc12b7764e3364)

diff --git a/docs/submodules/sdnvpn b/docs/submodules/sdnvpn
index e617bed..352c595 160000 (submodule)
--- a/docs/submodules/sdnvpn
+++ b/docs/submodules/sdnvpn
@@ -1 +1 @@
-Subproject commit e617beda206166f291433f58081e48ac50e48dbb
+Subproject commit 352c59535785950f9af57838ceaced3b040ca238