Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge changes from topic 'convert-sla-asserts-to-raises'

    * changes:
      Replace MagicMocks with Mocks from SearchRunner UTs
      Add vsperf_dpdk SLA validation unit test cases
      Cleanup vsperf unit tests

  - Replace MagicMocks with Mocks from SearchRunner UTs

    This patch replaces unneeded MagicMocks with Mocks from TestSearchRunner
    and TestSearchRunnerHelper.

    JIRA: YARDSTICK-1169

    Change-Id: I30a7bbc71c0b1062e6c0dfe634a5a8f1ecb7c684
    Signed-off-by: Miikka Koistinen <miikka.koistinen@nokia.com>
  - Add vsperf_dpdk SLA validation unit test cases

    JIRA: YARDSTICK-1228

    Change-Id: Ic32f2bcd7f8bdf718c9c266666409d32ecab4924
    Signed-off-by: Miikka Koistinen <miikka.koistinen@nokia.com>
  - Cleanup vsperf unit tests

    Remove unneeded mock return values and improve the test execution.

    Add unit test cases about SLA validation.

    JIRA: YARDSTICK-1227

    Change-Id: I90b8b9c4cb6a57ae4b0869e84af0da43ee22a670
    Signed-off-by: Miikka Koistinen <miikka.koistinen@nokia.com>