Update git submodules

Update git submodules

* Update docs/submodules/apex from branch 'stable/danube'
  - Removes neutron ovs agent systemd when not nosdn

    Bug in ovs agent systemd where it is started when openvswitch is
    restarted.  This is causing ODL DPDK deployments to fail because
    openvswitch is creating br-int as type system instead of netdev.

    JIRA: APEX-427

    Change-Id: Iea7f6a5553d2ca1f372f4dec82f576d62827e887
    Signed-off-by: Tim Rozet <trozet@redhat.com>
    (cherry picked from commit 2ea2ee214210f1eec14c8bdf91260ee883eb3192)