Update git submodules

Update git submodules

* Update docs/submodules/releng-xci from branch 'master'
  - bifrost: bifrost-provision.sh: Always initialize XCI_ANSIBLE_VERBOSITY

    The XCI_ANSIBLE_VERBOSITY is normally exported by the XCI bootstrapping
    process. However, sometimes it's necessary to run bifrost-provision.sh
    by itself so we can debug machine provisioning. As a result of which,
    we need to initialize this variable properly so we don't fail with
    'unbound variable' errors.

    Change-Id: I81c59cf8eb3369c001e952c2c0a2846ed8d95cdf
    Signed-off-by: Markos Chandras <mchandras@suse.de>