Update git submodules

* Update docs/submodules/samplevnf from branch 'stable/euphrates'
  - Merge "Fix udp replay issue" into stable/euphrates
  - Fix udp replay issue

    Change-Id: Ibb269fdf4e2bccb56d96d1788ba62ebfcc96d267
    Signed-off-by: Deepak S <deepak.s@linux.intel.com>

diff --git a/docs/submodules/samplevnf b/docs/submodules/samplevnf
index f778dd1..e511ac9 160000 (submodule)
--- a/docs/submodules/samplevnf
+++ b/docs/submodules/samplevnf
@@ -1 +1 @@
-Subproject commit f778dd110d907a05c8279d97839a652ae4a84796
+Subproject commit e511ac90dd0415ae4c57e6b0c706cfb8a051c081