Update git submodules

Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Merge "SNAPS tests now support offline testing."
  - SNAPS tests now support offline testing.

    Images by type (cirros, centos, ubuntu) can now have the download URL be
    overridden, told to leverage a local file, or have custom configuration
    when using the snaps.openstack.tests.openstack_tests.py image settings
    helper functions.

    JIRA: FUNCTEST-809

    Change-Id: I790094a7a26eb5a55f53d6e875c658dc5e7ac2f9
    Signed-off-by: spisarski <s.pisarski@cablelabs.com>