Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Add "duration" parameter to test case definition"
  - Add "duration" parameter to test case definition

    Add "duration" parameter to test case definition, in scenario:options
    section. This parameter will be rendered in the traffic profile.

    If the parameter is not present in the test case scenario options, the
    default time written in the traffic profile options will be 30 seconds
    (TrafficProfile.DEFAULT_DURATION = 30). If the traffic profile
    injection time is not defined, the default injection time will be 30
    seconds.

      testcase:scenario:options:duration (default = 30)
          render --> traffic_profile:duration
              parse --> TrafficProfile.duration (default = 30)

    Target traffic profiles (RFC2544):
      - RFC2544Profile
      - IXIARFC2544Profile

    JIRA: YARDSTICK-1194

    Change-Id: I968922e6bb882d7ee15aa1c4db4037face7a3492
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>