Update git submodules

Update git submodules

* Update docs/submodules/dovetail from branch 'master'
  - Remove one sub test case from dovetail.tempest.tc004

    1. Currently, dovetail.tempest.tc004 has 13 sub test cases defined in its
       config file and specification document of the test case. All these
       sub test cases are picked from tempest based on it's version 15.0.0.
    2. For Dovetail 1st release, it fixes the version of Functest to be
       opnfv/dovetail:cvp.0.5.0, and Functest integretes tempest 14.0.0
       in this version and it's E release.
    3. There is one sub test case in dovetail.tempest.tc004 that is new in
       tempest 15.0.0, so it can not be recognized and executed by Functest D
       and E release. It is 'test_server_connectivity_cold_migration_revert'.
    4. Remove this sub test case from dovetail.tempest.tc004. This means remove it
       from the test case config file and specification document.

    JIRA: DOVETAIL-561

    Change-Id: Ia927af040794c7027a741a282ed75fe401f99ff1
    Signed-off-by: xudan <xudan16@huawei.com>