Update git submodules

* Update docs/submodules/samplevnf from branch 'master'
  - Merge "Add support for generation of jumbo frames"
  - Add support for generation of jumbo frames

    Change-Id: I63af4e5c5c01a4412d517e33fc7111481fd0524a
    Signed-off-by: Xavier Simonart <xavier.simonart@intel.com>

diff --git a/docs/submodules/samplevnf b/docs/submodules/samplevnf
index e12ec1f..509c3f8 160000 (submodule)
--- a/docs/submodules/samplevnf
+++ b/docs/submodules/samplevnf
@@ -1 +1 @@
-Subproject commit e12ec1f7d2b4fe8c28650e6cd53cae660ea96ec1
+Subproject commit 509c3f840b4afb659e344e2d373d0f9052c1c7bf