Update git submodules

Update git submodules

* Update docs/submodules/so.git from branch 'master'
  to dca9a2db304b2ac196ec16c1bec08e9df9cd6a22
  - Merge "Add method to send message to Camunda engine"
  - Add method to send message to Camunda engine

    Issue-ID: SO-2368

    Modify CamundaRequestHandler to add method to send
    message to Camunda engine. Use non-blocking webclient
    considering workflow may take long time to finish.

    Change-Id: I70a8b38881ac40b4d65a3d7305f57a56829e6f1d
    Signed-off-by: Harry Huang <huangxiangyu5@huawei.com>