Update git submodules

* Update docs/submodules/apex from branch 'stable/danube'
  - Enable OpenDaylight clustering mode for FDIO scenarios

    JIRA: APEX-450

    Change-Id: I6d570c19ff5286b1307e38eee439116839b1d612
    Signed-off-by: Feng Pan <fpan@redhat.com>

diff --git a/docs/submodules/apex b/docs/submodules/apex
index aaa6cad..baaa7ac 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit aaa6cad0c1247d5f062bedaedc8df438fc02f746
+Subproject commit baaa7ac3cdc7984c97a4e1873ad118969ba95a01