Update git submodules

* Update docs/submodules/nfvbench from branch 'stable/euphrates'
  - Harmonization of the titles of the Testing documents

    Change-Id: I7917fb361063e7aad65c193e05a5aa5ef175059b
    Signed-off-by: Morgan Richomme <morgan.richomme@orange.com>

diff --git a/docs/submodules/nfvbench b/docs/submodules/nfvbench
index d5c0e0a..c73860d 160000 (submodule)
--- a/docs/submodules/nfvbench
+++ b/docs/submodules/nfvbench
@@ -1 +1 @@
-Subproject commit d5c0e0adeeaf80f4c6eefb24e70e94eca636173b
+Subproject commit c73860d3d36b718359a680cf2abd971aad47bec2