Update git submodules

Update git submodules

* Update docs/submodules/clover from branch 'master'
  - Merge "Adding cassandra service with a separate yaml file."
  - Adding cassandra service with a separate yaml file.

    - Left the file samples/scenarios/service_delivery_controller_opnfv.yaml unchanged.
    - Added a yaml definition of Cassandra StatefulSet and its service into a separate file under tools directory
    - Cassandra Service run with 1 replica
    - Deleted 'data-plane-ns' and use 'default' instead for cassandra containers.
    - Revoked changes for samples/scenarios/service_delivery_controller_opnfv.yaml.
    - Added new line (Wutien suggested it)

    JIRA: CLOVER-000

    Change-Id: I2bb4249cf2523f5011d6fefc69dc469a90e20eaf
    Signed-off-by: iharijono <indra.harijono@huawei.com>