Update git submodules

Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Define DOCKER_TAG in Functest daily job

    It defines DOCKER_TAG as parameter in Functest daily job.
    It also fixes DOCKER_TAG default value in properties files and then
    complete the previous commit [1].

    It should fix the current gate issues [2].

    [1] https://gerrit.opnfv.org/gerrit/#/c/64069/
    [2] https://build.opnfv.org/ci/view/functest/job/functest-apex-baremetal-daily-gambia/18/console

    Change-Id: Ia531ca68a455cc20294e123286062265b9b79d6f
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>