Update git submodules

Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "prototypes: xci: Add ability to use local repositories for testing"
  - prototypes: xci: Add ability to use local repositories for testing

    When developing XCI features it's useful to be able to use the local
    repositories rather than cloning them from git since that makes
    it harder to test local modifications against XCI. As such, we add
    three new variables which can be used to hold local paths to the
    bifrost, releng and openstack-ansible repositories. We are still
    cloning the repositories but we then use the 'synchronize' Ansible
    module to copy modified files from the local repositories.

    Change-Id: I6d593ea48d8b9c51415d9d0848f77a498ef2f486
    Signed-off-by: Markos Chandras <mchandras@suse.de>