Update git submodules

Update git submodules

* Update docs/submodules/releng-xci from branch 'master'
  - Merge "Add tacker to the list of components to install"
  - Add tacker to the list of components to install

    Tacker is already part of the upstream setup-openstack.yml but as releng-xci
    overwrites it, tacker does not get deployed. Adding it to the
    setup-openstack.yml of releng-xci does not disturb the other scenarios as it
    will only be deployed when the tacker container is defined which only happens
    when deploying odl-sfc

    Change-Id: Ifd76fc49369c114c55e966eb20658d82c99e14cb
    Signed-off-by: Manuel Buil <mbuil@suse.com>