Update git submodules

* Update docs/submodules/apex from branch 'stable/danube'
  - Moving undercloud root pw to debug only

    Change-Id: I380d39b6c78519487dec3b053c53a9579df57f06
    Signed-off-by: Dan Radez <dradez@redhat.com>
    (cherry picked from commit 035c80d52a780125ba84d1bc5f8232c9ff2a4a17)

diff --git a/docs/submodules/apex b/docs/submodules/apex
index 55427ec..b7c0066 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit 55427ec21a17cd601a4abb2cab4de4694ba1a702
+Subproject commit b7c0066de509b3eb2e1264966eff12cff49472e1