Update git submodules

* Update docs/submodules/functest from branch 'stable/danube'
  - Logger must be a singleton

    It avoids creating a python object for every message printed.

    Change-Id: Ia42b59db9f7ce4eadc7e91da4d193db646b54d85
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>
    (cherry picked from commit 0acb8eb018afd993c363c05da8a45091abc59fd9)

diff --git a/docs/submodules/functest b/docs/submodules/functest
index 2c48dfc..555d754 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit 2c48dfc2b32c577c4754c2f1df2e6becc9bf5af3
+Subproject commit 555d7546711b67197c9daeb87e8a0415203b3b88