Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "NSBperf: don't exit during import time"
  - NSBperf: don't exit during import time

    This was breaking testr unittests.

    Don't do this like this during import time,
    only do them in if __name__ sections, otherwise
    when anything else tries to import this module
    it exists.

    Change-Id: Ia17f5e1a5cbe07ab287d3b95e96489b8a6248170
    Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>