Update git submodules

Update git submodules

* Update docs/submodules/dovetail from branch 'master'
  - Change the directories of results and some files to DOVETAIL_HOME

    JIRA: DOVETAIL-438

    1. Need an env variable DOVETAIL_HOME in env_config.sh
    2. env_config.sh, pod.yaml and id_rsa should be put in path DOVETAIL_HOME/pre_config
    3. the results will also be put in this path
    4. no need to give the path of openstack credential file while running a testsuite
    5. if running with the code, source the env_config.sh file before running
          source $DOVETAIL_HOME/env_config.sh
          dovetail run --testsuite <testsuite_name>
    6. if running with Dovetail docker image
          docker run -it --privileged=true -e DOVETAIL_HOME=<dovetail_home_path>
                 -v <dovetail_home_path>:<dovetail_home_path>
                 -v /var/run/docker.sock:/var/run/docker.sock
                 opnfv/dovetail:latest /bin/bash

    Change-Id: Ia23078f27a34e293d0075e49c673930f41069cb6
    Signed-off-by: xudan <xudan16@huawei.com>