Update git submodules

* Update docs/submodules/apex from branch 'stable/euphrates'
  - Increase ssh timeout and add retry for Ansible

    Several users have experienced random disconnections from the undercloud
    during deployment.  This should help to stop deployments from aborting.

    Change-Id: Idb7619d493b329944f21ea6641f6826a8fcc3907
    Signed-off-by: Tim Rozet <trozet@redhat.com>
    (cherry picked from commit 0fc3c2190ad304052d0ec210c94ab3f09e95b71d)

diff --git a/docs/submodules/apex b/docs/submodules/apex
index 551dac3..6ddb7d3 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit 551dac3e8cf9c1fdd050ccaf4e8d79d946586d52
+Subproject commit 6ddb7d379156ba03c9c4bdcb01679d6727cb4dd6