Update git submodules

* Update docs/submodules/nfvbench from branch 'stable/euphrates'
  - Add missing license text

    Change-Id: I9267e1f519f7c433df3ba139d397aaabf5fb45a0
    Signed-off-by: ahothan <ahothan@cisco.com>

diff --git a/docs/submodules/nfvbench b/docs/submodules/nfvbench
index 695b6a5..f872621 160000 (submodule)
--- a/docs/submodules/nfvbench
+++ b/docs/submodules/nfvbench
@@ -1 +1 @@
-Subproject commit 695b6a59490b7438f534f0f13606b9084922ec95
+Subproject commit f872621f345c1fa5d7cbbc1da20ca0eb2c185976