Update git submodules

Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Get properly env vars or their default values

    It defines env.get() as an unique way to get Functest env vars or
    their default values. It can be considered as a wrapper above os.environ.

    It enforces backward compatibility via CONST which mustn't be used
    for that purpose. It should be noted that it also stops using CONST
    for getting OpenStack env vars.

    Change-Id: I333dc1afbc0123166a7eaff8b551370098efa341
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>