Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Refactor remote command execution in vsperf"
  - Refactor remote command execution in vsperf

    * Remove unneeded variables
    * Do not raise RuntimeError when a remote command fails, instead leave
      it for the yardstick ssh module to handle.
    * Prevent CsvReader from raising StopIteration if csv output cannot be
      parsed. The SLA validation will take care of errors in that case.

    JIRA: YARDSTICK-1166

    Change-Id: I6cf550bd7bc8f511b3c0f25c67f8caab18bccd28
    Signed-off-by: Miikka Koistinen <miikka.koistinen@nokia.com>