Update git submodules

* Update docs/submodules/functest from branch 'stable/euphrates'
  - Update Functest documentation for Euphrates

    - Better description of Alpine docker (default artifact)
    - Reorganization of config and user guide
    - Upgrade of the developer guide

    Change-Id: Ie8e10f027bfcdb01c992cd161a1af2d6d6e29536
    Signed-off-by: Morgan Richomme <morgan.richomme@orange.com>
    (cherry picked from commit 5504724dc69096b36948de9bd07b82f5058242f0)

diff --git a/docs/submodules/functest b/docs/submodules/functest
index b45746e..21d8ff3 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit b45746ee8dcf62cf11b860e4c4b797779a08abc7
+Subproject commit 21d8ff3fb13dac52cb3e906e968ee69104012082