Update git submodules

Update git submodules

* Update docs/submodules/multicloud/k8s.git from branch 'master'
  to 251c38778c0c499cae61383720dd8b053b16b87e
  - Handle uncommon format of proper tar archive

    Provide proper handling of tar archives containing
    "current directory", but stored in format:
    ```
    .
    file2.txt
    dir1/
    dir1/file1.txt
    ```
    instead of typical:
    ```
    ./
    ./file2.txt
    ./dir1/
    ./dir1/file1.txt
    ```

    Issue-ID: MULTICLOUD-1025
    Signed-off-by: Konrad Bańka <k.banka@samsung.com>
    Change-Id: Ideffd019255a9f2d029527066e5a6a03d45a2d7b