Update git submodules

* Update docs/submodules/nfvbench from branch 'stable/euphrates'
  - StatsManager must clean up self when there is an exception in __init__

    ALso remove unused connection.py

    Change-Id: I1bf688ade511f2054e9d67edf8938df1988e4cb2
    Signed-off-by: ahothan <ahothan@cisco.com>

diff --git a/docs/submodules/nfvbench b/docs/submodules/nfvbench
index ca96a3a..a304887 160000 (submodule)
--- a/docs/submodules/nfvbench
+++ b/docs/submodules/nfvbench
@@ -1 +1 @@
-Subproject commit ca96a3aa9ccb88f2b041506b46bb628df74e64f8
+Subproject commit a304887b78e7d3d4786ecbe367c681d2f5d3926a