Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Update pmd/lcore mask for OVS-DPDK context"
  - Update pmd/lcore mask for OVS-DPDK context

    Added default values for pmd/lcore mask to the SampleVNF test case for
    Trex TG.
    lcore mask - specifies the CPU cores used for non-datapath OVS-DPDK
    threads.
    pmd mask - specifies the CPU cores used for data path packet processing.
    Updated documentation for Standalone OVS-DPDK context.

    JIRA: YARDSTICK-1246

    Change-Id: I8d008a185c94d2047ffa4769d7974bc4d283fd7f
    Signed-off-by: Stepan Andrushko <stepanx.andrushko@intel.com>