Update git submodules

Update git submodules

* Update docs/submodules/sdnvpn from branch 'stable/euphrates'
  - Adapt bgp daemon to run properly for testcase3

    Since apex includes a new version of zrpcd compatible with Carbon
    and Nitrogen [0], an adaptation is needed for bgp daemon enabling
    and running within testcase3

    Note that zrpcd run now as a process and not as a service

    JIRA: SDNVPN-172

    [0] https://jira.opnfv.org/projects/APEX/issues/APEX-508

    Change-Id: Ia0ec4ab0f15ecf3d5c76c5fa541fe8338762ecaf
    Signed-off-by: tomsou <soth@intracom-telecom.com>
    (cherry picked from commit e1372d3c4955a92f36bfb50ae5925dac2fc0b89c)