Update git submodules

Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "[builde servers] Update manifest-tool URL"
  - [builde servers] Update manifest-tool URL

    The fact returned for 'ansible_architecture' is 'x86_64' for non-ARM
    servers. Hard coding this now in order to pull the correct URL of the
    manifest tool.

    When arm build servers are included in this list we'll set a fact for
    the architecture needed in the URL.

    Change-Id: I1c89e8a87cc7f2ae386973f3f1088f881ae5df71
    Signed-off-by: Trevor Bramwell <tbramwell@linuxfoundation.org>