Update git submodules

Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Clean requirements.txt

    It removes all requirements which are not detected by pipreqs [1]
    except:
      - robotframework-httplibrary
      - robotframework-requests==0.4.7
      - robotframework-sshlibrary==2.1.3

    They seem indirectly required for the next ODL suites: old_netvirt
    and fds.

    It also defines pbr as requirement and orders dnspython3 conditions.

    [1] https://github.com/bndr/pipreqs

    Change-Id: Idcd01296e5a5862ff8528dc083468b5c4905c9f9
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>