Update git submodules

Update git submodules

* Update docs/submodules/releng from branch 'master'
  to 2a6b3b809ec3127479f69dd8831e8c7b8ea5fb19
  - Deactivate a few Functest tests in Airship gates

    This tests should be part of gating but Airship is not good enough to
    allow running them. It avoids voting -1 in all Airship tests.

    They are only temporarily removed in gates and they will be executed
    as soon as possible (git revert).

    Change-Id: I524cb9ab8aa09bfd3413caab9c65e103372a359c
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>