Update git submodules

* Update docs/submodules/functest from branch 'stable/euphrates'
  - Force python2 when creating venv for refstack

    python3 has been selected since it was installed for doctor [1].

    [1] https://gerrit.opnfv.org/gerrit/#/c/41823/

    JIRA: FUNCTEST-875

    Change-Id: I942122b46dc0ebe594306877f5a0350f876d7c01
    Signed-off-by: Linda Wang <wangwulin@huawei.com>
    (cherry picked from commit f36d607e1b8f7660bbcb4c06d589d4eeb76158e3)

diff --git a/docs/submodules/functest b/docs/submodules/functest
index b9b8b9a..f83d853 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit b9b8b9a0b24aac1d38e13f9c5b0e1fdebc995894
+Subproject commit f83d8530bf34c1f2aa29fef0a3030a11a9ed4fa7