Update git submodules

Update git submodules

* Update docs/submodules/releng from branch 'master'
  to 8a085c67653970f6078352808cbcf5eb4fcbce72
  - Merge "Revert "Remove offline slaves""
  - Revert "Remove offline slaves"

    There was no comment or discussion as to why this patch was proposed or
    merged. These agents need to be included in the list and the job
    scheduled or else disks space fills up with old docker images, knocking
    the agent offline.

    This reverts commit 9d245364f1a4390700f077a9cbd20542f859151e.

    Change-Id: Ie95ad04a409777d22d9c436f48690e864255f2bf
    Signed-off-by: Trevor Bramwell <tbramwell@linuxfoundation.org>