Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "cleanup: rm node_ID from yardstick prepare_env file"
  - cleanup: rm node_ID from yardstick prepare_env file

    There is some redundant code in prepare_env.sh script
    for the fuel installer, the changes are to:

    1. Remove variabls 'node_ID' and 'node_line_num';
    2. Rewrite section that replace ip address of controller/compute;
    3  Add $YARDSTICK_REPO_DIR in front of variable 'pod_yaml';

    JIRA: YARDSTICK-991

    Change-Id: I4fbd2c2ba2e6109cc04dc452202fbed701d79b2b
    Signed-off-by: ting wu <ting.wu@enea.com>