Update git submodules

* Update docs/submodules/functest from branch 'stable/euphrates'
  - Remove stable docker tags

    Releng and travis-ci jobs don't publish any stable tags, then they
    should be removed from Docker automated builds as well.

    It will be completed by removing all former tags by hand as well to
    avoid mixing euphrates and these deprecated tags.

    Change-Id: I969e5313ca29edee0a1bfd534ff45a5c09183816
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/functest b/docs/submodules/functest
index e9bb037..a6f29f8 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit e9bb037713e5921fe464abc43380bc995003c4c9
+Subproject commit a6f29f8d093a1a88a936c2beaecc56aeca6a3901