Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Merge "Add xtesting in upper-constraints.txt"
  - Add xtesting in upper-constraints.txt

    functest-kubernetes requires xtesting and still reads this file.

    Change-Id: I18d357cc88ae9a7e80aca568d408823291dc2ab3
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/functest b/docs/submodules/functest
index ff087a1..336b921 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit ff087a1234a0ef39f5994d53e708a6020ab906b6
+Subproject commit 336b921e51e7910226a410189fc9cc34e8e988df