Update git submodules

Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "Multiple Dockerfile Builds per Project"
  - Multiple Dockerfile Builds per Project

    Instead of defining docker build jobs in terms of projects, we define
    them in terms of dockerrepos. Each dockerrepo is associated with a
    specific project and may have a seperate Dockerfile (which defaults to
    'Dockerfile' if unspecified), and location for files needed by the
    Dockerfile (default: 'docker').

    This should allow for running multiple docker builds out of a single
    project repository without having to modify the current docker build
    scripts.

    The output of this job configuration should match what is currently in
    Jenkins.

    Change-Id: I9089d57a0c7cc56be4225b56e96bec56be258f1f
    Signed-off-by: Trevor Bramwell <tbramwell@linuxfoundation.org>