Update git submodules

* Update docs/submodules/apex from branch 'stable/danube'
  - add onos deployment steps

    opnfv-tht-pr: 128
    opnfv-puppet-tripleo-pr: 23

    Change-Id: Ib99f7e3968ed03bd86ca0de9c6c37c9871921486
    Signed-off-by: bobzhou <bob.zh@huawei.com>
    (cherry picked from commit 266e9a5336defeff5f10331ab8316d69e7b20cc1)

diff --git a/docs/submodules/apex b/docs/submodules/apex
index b5e4091..df55960 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit b5e4091424ced384b49f6ff13b1ef2b63466f947
+Subproject commit df5596005c4f0a98c39375feef0bcca55c89f239