Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Assign IXIA ports in one call instead of one by one

    Assigning IXIA ports one by one takes more time than
    assign all ports by once. Also, assigning ports in
    one call resolves the assign port issues caused on
    some IXIA chassis versions.

    JIRA: YARDSTICK-1425

    Change-Id: Ibb08e40ee1a8762573f6752bdd1f583c5a1d9d2a
    Signed-off-by: Mytnyk, Volodymyr <volodymyrx.mytnyk@intel.com>
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>