Update git submodules

Update git submodules

* Update docs/submodules/releng-xci from branch 'master'
  - xci: Make it easier to use OpenStack-Ansible stable branches

    It seems it is desirable for projects to use stable OpenStak-Ansible and
    OpenStack releases in general. However, merely overriding
    OPENSTACK_OSA_VERSION doesn't work because role requirements and
    OpenStack services have to be adapted too. Despite the Documentation
    warning users about this, seems like nobody remembers to read and
    do the necessary steps. However, this leads to numerous invalid bug
    reports due to this stable/master mix. Lets try to help improving
    this situation by doing all the necessary ground work if we detect that
    we are using a stable branch.

    Change-Id: I2ba5d7e7942109973b6a6523aae2c01b65e61fe7
    Signed-off-by: Markos Chandras <mchandras@suse.de>