Update git submodules

* Update docs/submodules/sdnvpn from branch 'master'
  - testcase execution halt fix

    It's found that sys.exit is used in utils.py which caused testcase
    execution is stopped abruptly while running bgpvpn testsuite.
    This is now replaced with Exception.

    Change-Id: I69df4be705985994318f58d57b152d6db4087610
    Signed-off-by: Periyasamy Palanisamy <periyasamy.palanisamy@ericsson.com>

diff --git a/docs/submodules/sdnvpn b/docs/submodules/sdnvpn
index 6a8c7ac..90204b0 160000 (submodule)
--- a/docs/submodules/sdnvpn
+++ b/docs/submodules/sdnvpn
@@ -1 +1 @@
-Subproject commit 6a8c7ac31bbf7c93ce971c216528fb609641b0d9
+Subproject commit 90204b0850c38e2c9eeb2cbb4dfccc2053beafb4