Update git submodules

Update git submodules

* Update docs/submodules/releng-xci from branch 'master'
  - Merge "xci: Drop OPNFV_RELENG_DEV_PATH variable"
  - xci: Drop OPNFV_RELENG_DEV_PATH variable

    The OPNFV_RELENG_DEV_PATH variable was used to point to a releng-xci
    development repository. However, people normally set the current
    directory as the development one and they almost always want to
    test the current code in XCI. Using an secondary releng-xci tree
    as development repo is a very obscure case and it normally complicates
    things. As such, let drop this option and always use the current
    repository for development purposes.

    Change-Id: If111bf29a32a5f6ea28694f191645af0c6a87abc
    Signed-off-by: Markos Chandras <mchandras@suse.de>