Update git submodules

* Update docs/submodules/functest from branch 'stable/euphrates'
  - Remove void return value mocks in rally unit tests

    Change-Id: I369b98fb9120830b1868f438c7da2a039a60d890
    Signed-off-by: Juha Kosonen <juha.kosonen@nokia.com>
    (cherry picked from commit 31524290992dad02d5ca1e6b17304bf31b56b7f7)

diff --git a/docs/submodules/functest b/docs/submodules/functest
index 77b1231..d684b8a 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit 77b1231c610a659ca6e782c9297b4a0d918eb97f
+Subproject commit d684b8aa0aa0aaa600095b92b4203302b5a57972