Update git submodules

Update git submodules

* Update docs/submodules/dovetail from branch 'master'
  - Merge "WIP: Test case description for vping test cases"
  - WIP: Test case description for vping test cases

    Adding test case descriptions for both vping test cases implemented in
    Functest. Test case 1 makes use of the config drive mechanism of
    Nova to pass a test script. Test case 2 uses SSH to transfer and execute
    a script on one VM.

    Change-Id: Ic8be6ad4dfd4b0e7661064506b0ae92db2fc1463
    Signed-off-by: Georg Kunz <georg.kunz@ericsson.com>