Update git submodules

Update git submodules

* Update docs/submodules/dovetail from branch 'master'
  - Updating user guide with new ssh key config in pod.yaml

    Dovetail does not copy the ssh key from pre_config to /root/.ssh anymore
    inside Yardstick but instead, we point the pod.yaml file directly to the
    key inside the pre_config directory.

    JIRA: DOVETAIL-655

    Change-Id: I23156d8940194547363bcf9a5cc581aab0d5c640
    Signed-off-by: Georg Kunz <georg.kunz@ericsson.com>