Update git submodules

* Update docs/submodules/apex from branch 'master'
  - Merge "Updates to create_vm for aarch64"
  - Updates to create_vm for aarch64

    - serial console was being duplicated in libvirt xml template
    - force undercloud VM arch to jumphost arch
    - assign diskbus to scsi for aarch64

    Change-Id: I5208883c2001497fc7e958f9ffcdf14f0be5f600
    Signed-off-by: Dan Radez <dradez@redhat.com>

diff --git a/docs/submodules/apex b/docs/submodules/apex
index 0c78953..6a4cd2f 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit 0c78953b8184255eba2c55316bc6cbb746796a5f
+Subproject commit 6a4cd2fe76fe445394cd92c3f0e9486084b53489