Update git submodules

Update git submodules

* Update docs/submodules/releng from branch 'master'
  to e1f021c2d45e25e1ab13637f410d325f934bcd15
  - Try to get best parallel testing values

    It's no simple to get the best threads (test cases and tempest) values
    and then guarantee Functest vs:
      - test flapping
      - backend limitations

    As opposed to the OpenStack gates, Jenkins runs all test cases in
    parallel which indirectly increases the number of threads.

    Let's run smoke sequentially which is closed to the OpenStack model.

    Change-Id: I6172568b915d49e2723173b7c428970110f63620
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>