Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Remove Tempest repo and use the one created by Refstack

    Refstack clones the repo in /home/opnfv/.tempest. Rally can use
    that repo which is checked out to the REFSTACK_TAG=15.0.0
    This way, we avoid having twice the same files.

    Change-Id: I9b05d29b1c9bdf3d10539b771d0d20abb2b7cc37
    Signed-off-by: jose.lausuch <jose.lausuch@ericsson.com>

diff --git a/docs/submodules/functest b/docs/submodules/functest
index 3409bc4..c052d52 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit 3409bc4eaf88b78e15b045afbd6b461c3fb281e7
+Subproject commit c052d52d30bb4aad229fef04560a3f71dff0cab5