Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Switch to $REPO in travis-ci jobs

    It conforms with "Use functest repo variable" [1]

    [1] https://gerrit.opnfv.org/gerrit/#/c/52513/

    Change-Id: I09b438d784fbeb5e3686b441e6944c87c0f88382
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/functest b/docs/submodules/functest
index 67e9875..ee83897 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit 67e9875d82d1ee2de3ed64d756092b1f5698c9c0
+Subproject commit ee838977750a9d23d02a710f7a41a02e8f0f24a4