Update git submodules

* Update docs/submodules/functest from branch 'stable/euphrates'
  - Fix "Broken pipe" IOErrors of rally run

    Replace obsolete os.popen with subprocess module usage in command
    output retrieval. Do not use shell as the program to execute.

    Change-Id: Ic63bb0f393750c3b85a35a37fecd46c1c1b96602
    Signed-off-by: Juha Kosonen <juha.kosonen@nokia.com>
    (cherry picked from commit 8335acdf080e4d31fd1dd70f11aa456b4795833a)

diff --git a/docs/submodules/functest b/docs/submodules/functest
index 777acd3..a508c43 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit 777acd341ff407838440dae3ed69291ec4c52626
+Subproject commit a508c431dd66aa86b27b06da716ffe6a8b63409c