Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Fixed few gaps when running on a minimal version of system"
  - Fixed few gaps when running on a minimal version of system

    - we need to make sure we have lsof installed
    - we need to update cache inside the image, because we are unable to install some of them

    Change-Id: Ic555489779e9096540001cb9c62ea2ab25c1ae90
    Signed-off-by: Maciej Skrocki <maciej.skrocki@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 3ef3ad6..661d78e 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 3ef3ad677461c9677c701ec19760cc47af9ff492
+Subproject commit 661d78e5ad9a831a4e6c36287d17ff6829b062d0