Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Rename test/unit/cmd directory"
  - Rename test/unit/cmd directory

    Renamed test/unit/cmd directory to test/unit/test_cmd, in order to
    avoid importing errors during the execution of unit tests. This directory
    name collides with Python "cmd" library.

    Change-Id: Ie06d58d4faace33df684c8e511a398aa0667b098
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 0182d47..c191b30 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 0182d472d35a78c460610f5e35018416f857059b
+Subproject commit c191b305790b4528868725db82d1af6c0d95e22b