Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Merge "download_images.sh: add --keep option to avoid redownloading images"
  - download_images.sh: add --keep option to avoid redownloading images

    Change-Id: Id25f1a354ffd067ba926dc67907b6ca913999437
    Signed-off-by: Morgan Richomme <morgan.richomme@orange.com>

diff --git a/docs/submodules/functest b/docs/submodules/functest
index 8245094..20f03e5 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit 8245094e48cd0b8b810e89120a51b0581b0d78e6
+Subproject commit 20f03e5678f7eb2280d8a0c0ec37b18a00a92e3b