Update git submodules

* Update docs/submodules/apex from branch 'stable/euphrates'
  - Enables br-ex on controllers in SFC scenario

    ODL's current behavior is to select a node to serve as the routing/L3
    node in a deployment.  The selection is random, and it could end up
    choosing a control node.  Therefore the control node needs to have
    external network connectivity so adding br-ex to the controller which
    will enable this via default ProviderMappings.

    JIRA: APEX-558

    Change-Id: Ie3044e5711ba62d73b83d69cde369e7452958844
    Signed-off-by: Tim Rozet <trozet@redhat.com>
    (cherry picked from commit 8b280f8faf98b3f69435ceab3d045aaac49ecb3e)

diff --git a/docs/submodules/apex b/docs/submodules/apex
index a59619f..c4e60fb 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit a59619ffee744562eaea49d11c51ccc8df40b7af
+Subproject commit c4e60fbca8cefc5c81d221c4faa55fed09f5e70c