Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Remove unused nova client functions."
  - Remove unused nova client functions.

    Following funtions are not required by shade client also
    not been used in any of the scenario files:
    *create_aggregate
    *create_aggregate_with_host
    *create_instance
    *add_host_to_aggregate
    *create_aggregate_with_host
    *get_availability_zones
    *get_availability_zone_names
    *remove_hosts_from_aggregate
    *remove_host_from_aggregate
    *delete_aggregate
    *get_image_by_name
    *check_status

    JIRA: YARDSTICK-1088

    Change-Id: I7ba0fbce6aa3e636aa55581a993c1ec1b48fbead
    Signed-off-by: Shobhi Jain <shobhi.jain@intel.com>