Update git submodules

Update git submodules

* Update docs/submodules/dovetail from branch 'master'
  - Test case descriptions for Tempest smoke tests

    Adding a high-level description of the Tempest smoke tests.
    As agreed on the last Dovetail call, we are aiming for a relatively low
    level of detail and instead point to available documentation. As the
    tests themselves are quite simple of read, this is the best,
    most concise, and up-to-date version of documentation we can find.

    JIRA: DOVETAIL-599

    Change-Id: I985592c55fd415e254e70db6c6480c7bf3670a29
    Signed-off-by: dimitris.tsiolakis <dmts@intracom-telecom.com>