Update git submodules

Update git submodules

* Update docs/submodules/releng-xci from branch 'master'
  - Merge "xci: scripts: Add script to use clean virtual machines for testing"
  - xci: scripts: Add script to use clean virtual machines for testing

    These scripts will prepare a clean OS image based on diskimage-builder
    and launch a new VM with it. The purpose of that is to use this virtual
    machine as a 'host' to run XCI on it. This way we can ensure that all
    tests are being executed on the same clean environment which is ideal
    for reproducing and debugging purposes. We also commit the ssh keypair
    so we can build it in the image and use it to control the virtual
    machine without user interaction. Needless to say that this keypair MUST
    NOT be used for anything else apart from the dib build process.

    Change-Id: Idec0fc06c82435adc1a4d569b8e578616998de5f
    Signed-off-by: Markos Chandras <mchandras@suse.de>