Update git submodules

Update git submodules

* Update docs/submodules/releng-xci from branch 'master'
  - Merge "xci: Fix warning about missing inventory file"
  - xci: Fix warning about missing inventory file

    We no longer have a global inventory file and we don't need one right
    now since the bootstrapping opearations happen on the localhost anyway
    so we could be explicit and get rid of the following warning:

    [WARNING]: Host file not found: inventory
    [WARNING]: provided hosts list is empty, only localhost is available

    Change-Id: I5cfe7b0971397665cf9eae9c54985c44c4506449
    Signed-off-by: Markos Chandras <mchandras@suse.de>