Update git submodules

Update git submodules

* Update docs/submodules/compass4nfv from branch 'stable/danube'
  - Change the default packages url from compass http server to opnfv artifacts

    JIRA: COMPASS-544

    Currently compass4nfv uses compass http server to store those packages used in
    building ISO. This is not propriate in OPNFV community. So we push all the packages
    into opnfv artifacts repo and change the package url used in compass to opnfv
    artifacts repo url.

    Change-Id: I9661f2d893767e18c037ba9de5f54933f48ce466
    Signed-off-by: Yifei Xue <xueyifei@huawei.com>
    (cherry picked from commit 5cee19684b16e80b131cc3b5441781a3c6a7f971)