Update git submodules

Update git submodules

* Update docs/submodules/releng-xci from branch 'master'
  - Download only the needed images for OpenStack Functest Healthcheck

    Some of the files needed by Functest are pretty big and it takes time
    to download them all so this change ensures that the files are needed
    by healthcheck is downloaded and the rest is not.

    Further changes are needed to make the list even smaller for smoke test
    but we need Functest guidance to identify which of them are needed for
    what testing. It could be done by having suite specific download_images.sh
    like download_images_healthcheck.sh, download_images_smoke.sh and so on.

    deploy-scenario:os-nosdn-nofeature
    installer-type:osa

    Change-Id: Ib2c5867adfad8097d1a084c39ad08cc4df2e4549
    Signed-off-by: Fatih Degirmenci <fdegir@gmail.com>