Update git submodules

Update git submodules

* Update docs/submodules/functest from branch 'stable/euphrates'
  - Merge "Publish Docker Slicing Presentation" into stable/euphrates
  - Publish Docker Slicing Presentation

    It published the presentation done in the Functest Breakout during
    last OPNFV Summit (2017 in Beijing) [1].

    Minor changes are planned to update it in a second change.

    Git now ignores pdf which may be generated via reveal.js.

    [1] http://testresults.opnfv.org/functest/dockerslicing/

    Change-Id: I2b6cf113c672320bf1bc34442bb267fd99012546
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>
    (cherry picked from commit cb52dd523c58a6567b53ea5b79169295e1471117)