Update git submodules

Update git submodules

* Update docs/submodules/apex from branch 'stable/danube'
  - Fixes OVS DPDK scenarios

    This fixes nosdn OVS DPDK scenarios to work with OVS 2.6.  It also adds
    support for the ODL DPDK scenario.  OVS DPDK configuration is done
    during preconfig on compute nodes.  All nodes make use of first boot
    script to get kernel params like hugepages.  The network settings are
    modified to use real nic names for the virtual network settings file.
    This is required due to a timing bug with os-net-config and using
    first-boot script.  The network settings file also contains the UIO
    driver to use with DPDK.

    JIRA: APEX-314

    opnfv-tht-pr: 117

    Change-Id: I46b6fca71ecec38981968133ba2411f64d7c6445
    Signed-off-by: Tim Rozet <trozet@redhat.com>