Update git submodules

* Update docs/submodules/functest from branch 'stable/fraser'
  - Bypass NoneType errors when creating router in rally

    It converts private subnet name to str as it's mandary till [1].
    It could be reverted as soon as [2] is merged in snaps.

    [1] https://gerrit.opnfv.org/gerrit/#/c/56091/
    [2] https://gerrit.opnfv.org/gerrit/#/c/56171/

    Change-Id: Ia728415207f8ecb5b5ac55982f82337c45671c4c
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>
    (cherry picked from commit f0870e3735324941f5bd77243f36f9214cd531ac)

diff --git a/docs/submodules/functest b/docs/submodules/functest
index 67a905a..406b8a6 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit 67a905abf5f14d1a28ae61c4f5f0c15250e85e0e
+Subproject commit 406b8a60f1d4f8fb9083c3c0972e07e6e7125c49