Update git submodules

Update git submodules

* Update docs/submodules/releng-xci from branch 'master'
  - Merge "xci: infra: bifrost: Define more XCI variables for bifrost jobs"
  - xci: infra: bifrost: Define more XCI variables for bifrost jobs

    This is similar to eeb906a553d6ddf70ffc5af1acadb33a13ff5990 ("xci:
    infra: bifrost: Set XCI_DISTRO if it's not defined") so we need to
    define more XCI variables if we are running the standalone bifrost
    jobs.

    Change-Id: I112cfbfdda677174bdb0d0afef73f035c74cb79e
    Signed-off-by: Markos Chandras <mchandras@suse.de>