Update git submodules

* Update docs/submodules/sdnvpn from branch 'stable/euphrates'
  - Fixing return value in tempest test suite

    The result processing framework of the SDNVPN project expects "FAIL" as
    value for failed sub-tests to determine the overall result. The value
    returned by the tempest sub-tests was "FAILED", causing incorrect
    reporting to Functest.

    Change-Id: I320e6f1fb1fc7ee540813e454484b11bd5b227b2
    Signed-off-by: Georg Kunz <georg.kunz@ericsson.com>
    (cherry picked from commit 97cff3c409ffff5abfbb341eff07a00c4f353941)

diff --git a/docs/submodules/sdnvpn b/docs/submodules/sdnvpn
index a2f6324..e66856b 160000 (submodule)
--- a/docs/submodules/sdnvpn
+++ b/docs/submodules/sdnvpn
@@ -1 +1 @@
-Subproject commit a2f632467606d479ad0b44a1884b9a28d8f87106
+Subproject commit e66856ba6b9275582aa4fc370d2b9abf48b5381f