Update git submodules

* Update docs/submodules/apex from branch 'stable/euphrates'
  - Adding apex/overcloud/* unittests

    Change-Id: I02cd512ba1ddaee2538bee7739e27b136112a0c6
    Signed-off-by: Dan Radez <dradez@redhat.com>
    (cherry picked from commit d158a48f4f10e9abb1403b1178b8c2f31b36e992)

diff --git a/docs/submodules/apex b/docs/submodules/apex
index f5ff4ff..6960788 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit f5ff4ff13a1ab3b45454268f1871a2ba5c4cd944
+Subproject commit 6960788c4d5124a2ee4b31aa36408a050618d95c