Update git submodules

* Update docs/submodules/samplevnf from branch 'stable/euphrates'
  - Adding Sample Heat template for VNFs

    This patch adds samplevnf openstack heat templates generated by
    yardstick

    Change-Id: I8ba527d7d44a54a39071faffb03e41cc8bb8906b
    Signed-off-by: Deepak S <deepak.s@linux.intel.com>

diff --git a/docs/submodules/samplevnf b/docs/submodules/samplevnf
index 2280f91..6f2d777 160000 (submodule)
--- a/docs/submodules/samplevnf
+++ b/docs/submodules/samplevnf
@@ -1 +1 @@
-Subproject commit 2280f91c9c4a2261f44e19dadb4f450ef6c92e77
+Subproject commit 6f2d777637cc6a16200790a04080a8a22fd4b780