Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Add rtd-requirements

    It's required by rtd which doesn't leverage on PBR.

    Change-Id: Ia7ac5ecbb626d5c8b4c9095a1238db55e20790b0
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/functest b/docs/submodules/functest
index 9008030..a72b43b 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit 90080307c68683f352be2cad48c8371c746d4788
+Subproject commit a72b43b2356625d680d46f5ada201fcfe6ab7222