Update git submodules

Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Merge "Take OpenStack's constraints into account"
  - Take OpenStack's constraints into account

    upper-constraints.txt contains a pinned list of the entire set of
    transitive requirements for OpenStack [1].

    We will add OPNFV's constraints as well for OPNFV projects and
    their requirements when they are ready.

    [1] https://specs.openstack.org/openstack/openstack-specs/specs/requirements-management.html

    Change-Id: I2e23584f957e4de191341800d24c8b2776ef9143
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>