Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Add a default value to protect add_images.sh

    It sets a default value to the optional env var: FUNCTEST_IMAGES_DIR

    Change-Id: Ib78af2aaee27470ad10b0979a68c09963091cbb6
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/functest b/docs/submodules/functest
index 26c6f1a..06d0e32 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit 26c6f1aefce88a11e241eea7f7bb9fa0d6795b4e
+Subproject commit 06d0e3210b1d53f936729a2b65f474864d46218e