Update git submodules

* Update docs/submodules/apex from branch 'stable/euphrates'
  - Adding unittests for undercloud.py

    Change-Id: I65d73f7a1ad27f319857a72b7d9f738b04318aa6
    Signed-off-by: Dan Radez <dradez@redhat.com>
    (cherry picked from commit 11be8e73043eeaa9ec18508410ec28faecbccc08)

diff --git a/docs/submodules/apex b/docs/submodules/apex
index 17c64de..1ffe380 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit 17c64de8f2d9c86c0f80df8dddf7831210f5234a
+Subproject commit 1ffe380a91d9751c480d3e9c344d412c49ad72d2