Update git submodules

* Update docs/submodules/samplevnf from branch 'stable/gambia'
  - Fix potential crash when shuffling mbufs

    Change-Id: I70de6345afc6a696906f006c1b0f44540ae4ecec
    Signed-off-by: Xavier Simonart <xavier.simonart@intel.com>

diff --git a/docs/submodules/samplevnf b/docs/submodules/samplevnf
index ade1ef1..2d86094 160000 (submodule)
--- a/docs/submodules/samplevnf
+++ b/docs/submodules/samplevnf
@@ -1 +1 @@
-Subproject commit ade1ef11e0c54bb782bea863721964c53024c8ea
+Subproject commit 2d8609495ff4a58ceae13746f067fec6b0d5cf03