Update git submodules

Update git submodules

* Update docs/submodules/dovetail from branch 'master'
  - Tips on update docker to right version, > 1.8

    JIRA: DOVETAIL-414

    Dovetail requires docker at version > 1.8, so add some validation in code, and also versions of client and server should match
    with each other, or there will be unpredictable errors.

    Gives a notice to user to decide whether to update the docker to the latest version(1.17)

    Change-Id: I1331f5c19943a73e8fe25f76bd21628233e556f3
    Signed-off-by: grakiss <grakiss.wanglei@huawei.com>