Update git submodules

Update git submodules

* Update docs/submodules/releng-xci from branch 'master'
  - Merge changes from topics 'copy-hidden-skip-verify', 'xci-cache-skip-verify'

    * changes:
      xci: scripts: start-new-vm.sh: Copy hidden files and directories
      xci: scripts: vm: Add ability to use cached images for clean VM

  - xci: scripts: start-new-vm.sh: Copy hidden files and directories

    Fix the rsync command to also copy the hidden files and directories.
    Copying the .git directory allows us to quickly inspect any file
    changes when investigating bug reports and other problems.

    Change-Id: I4e6feeea77d5c3b23362a216206c5970b4900169
    Signed-off-by: Markos Chandras <mchandras@suse.de>
  - xci: scripts: vm: Add ability to use cached images for clean VM

    Make it possible to use the hosted dib images from artifacts.opnfv.org
    instead of building a new one on every CI run. This way, we can reduce
    the time it takes to start the actual XCI deployment.

    Change-Id: Idb1f5e3929cc14502c3f7383a61d2fbd0a6eefaf
    Signed-off-by: Markos Chandras <mchandras@suse.de>