Update git submodules

Update git submodules

* Update docs/submodules/dovetail from branch 'master'
  - Test case description for BGPVPN Tempest API tests

    Adding test case descriptions for the BGPVPN API tests which are
    implemented as Tempest plugin in the networking-bgpvpn repository. These
    tests have already been integrated for Euphrates into Functest test and
    are hence a candidate for inclusion in the test scope of the OVP
    Euphrates release as extension of the existing SDNVPN test cases.

    JIRA: DOVETAIL-598

    Change-Id: Id8578ed1e198ddbde967793737c69a5940c22475
    Signed-off-by: Georg Kunz <georg.kunz@ericsson.com>