Update git submodules

Update git submodules

* Update docs/submodules/releng/builder from branch 'master'
  to a5327783587200e1ead0fa7d43f81bec51185a4b
  - Add packer job for Ubuntu 16.04 docker image

    Ubuntu 16.04 docker image is being used in releng/builder
    requires a packer job for image updates.

    Also reorder the templates and platforms variables
    to make it consistant across the file and asciibetically.

    https://github.com/opendaylight/releng-builder/blob/master/jenkins-config/clouds/openstack/odlvex/ubuntu1604-docker-2c-2g.cfg

    Change-Id: Ie16528b6e1b4ef333685e91cc6e8b6556dee6480
    Signed-off-by: Anil Belur <abelur@linuxfoundation.org>