Update git submodules

* Update docs/submodules/nfvbench from branch 'stable/euphrates'
  - NFVBENCH-32 Check nan result values before integer casting

    Change-Id: Ia675672b40f93d7503ebe5a355896a084e3d0cbf
    Signed-off-by: Kerim Gokarslan <kgokarsl@cisco.com>

diff --git a/docs/submodules/nfvbench b/docs/submodules/nfvbench
index 580dcb0..3bc8857 160000 (submodule)
--- a/docs/submodules/nfvbench
+++ b/docs/submodules/nfvbench
@@ -1 +1 @@
-Subproject commit 580dcb07fce694295be416a4dd4162d3be02c357
+Subproject commit 3bc88579e9eadeafe141dc3d7fff7765486a5ee6