Update git submodules

Update git submodules

* Update docs/submodules/sdnvpn from branch 'stable/danube'
  - Merge "Cleanup after testcase running" into stable/danube
  - Cleanup after testcase running

    After every testcase running cleanup neutron and nova elements:
     - Allocated floating IPs (nova)
     - Created instances (nova)
     - Created images (nova)
     - Created router-subnet interfaces (neutron)
     - Created gateaway routers (neutron)
     - Created routers (neutron)
     - Created subnets (neutron)
     - Created networks (neutron)
     - Created bgpvpns (neutron)

    JIRA: SDNVPN-145
    JIRA: SDNVPN-148

    Change-Id: Id6df004bb9d0d394e2cf39692b624607167c9a6c
    Signed-off-by: tomsou <soth@intracom-telecom.com>
    (cherry picked from commit de80ee56c458b127be3497f3882bc1c962f42dfe)