Update git submodules

Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Skip Snaps testcases when OpenStack Rocky

    Snaps is testing vs OpenStack Queens following the traditional
    release track. Then Snaps testcases must be skipped vs OpenStack
    master as deployed by Apex.

    Snaps isn't compatible yet with the last Cinder changes (API
    microversions) which is out of its current scope [1].

    [1] http://artifacts.opnfv.org/logs/functest/lf-pod1/2018-07-19_05-29-02/functest.log

    Change-Id: I1e93527d9c87eb11bf7fd0cc9d04597614d32370
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>
  - Add helpers to detect OpenStack versions

    It leverages on Nova API Microversions [1].

    [1] https://docs.openstack.org/nova/latest/reference/api-microversion-history.html

    Change-Id: I60abf9089036e56fcbcd6c2b734666ea20875ceb
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>