Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Update heat RFC2544 based TC to support SRIOV VF ports."
  - Update heat RFC2544 based TC to support SRIOV VF ports.

    Updated vfw/tc_heat_rfc2544_ipv4_1rule_1flow_64B_trex.yaml TC to be
    able to run it in heat context with SRIOV VF ports configured in
    OpenStack.

    E.g.:
      yardstick task start --task-args='{"provider": "sriov"}' ...
      yardstick task start --task-args='{"provider": "sriov"}\
        physical_networks: ["physnet1", "physnet2"]}' ...

    Console log: http://paste.openstack.org/show/666931/
    Result output: http://paste.openstack.org/show/666930/

    JIRA: YARDSTICK-1004

    Change-Id: If0dabd0791e4e295782fee0f3de1536474218876
    Signed-off-by: Mytnyk, Volodymyr <volodymyrx.mytnyk@intel.com>