Update git submodules

Update git submodules

* Update docs/submodules/clover from branch 'master'
  - Add clover initial docker image build script

    - install dependent deb/pip packages
    - install basic tools istioctl, kubectl
    - install clover source code
    - build/upload docker image script
    - update requirements.txt
    - update module import path

    - To use this image use need setup kube-config file.
        e.g. `docker run -v /root/config:/root/.kube/config -it clover bash`

    Change-Id: I91044bb99ce8e2b785ef03212d961a97b3d42233
    Signed-off-by: QiLiang <liangqi1@huawei.com>