Update git submodules

Update git submodules

* Update docs/submodules/sdnvpn from branch 'master'
  - Create and pass references of flavor and image to tempest

    When invoked from SDNVPN, Tempest scenario functest test cases
    try to use flavor and image references from the tempest.conf file
    which are currently empty.
    This patch uses the default flavor that is created by the test
    suite and the creates an image using the availabe cirros image,
    which is deleted at the end.

    JIRA: SDNVPN-209

    Change-Id: I6a6fd636fec2c0fa7d35981ca51d59f06a4d9d69
    Signed-off-by: nikoskarandreas <nick@intracom-telecom.com>