Update git submodules

* Update docs/submodules/yardstick from branch 'stable/fraser'
  - Merge "Set "cmd2" library to version 0.8.6" into stable/fraser
  - Set "cmd2" library to version 0.8.6

    Last "cmd2" version, 0.9.0, removed Python 2+ support [1]. In order to
    support Python 2.7, version 0.8.6 (or earlier) must be installed.

    [1] https://github.com/python-cmd2/cmd2/commit/e54e5a5b891548df4df0acb04b6e607ad8f871b1

    JIRA: YARDSTICK-1205

    Change-Id: Ic2fe57438720de5b21c75f9456e653c6facf3ae9
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>
    (cherry picked from commit c4d821c58858418ce8dfec95426f06ae11b25c7b)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 578049f..caeb546 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 578049f6e4441d623b4345489204ad781465227e
+Subproject commit caeb546cd74b2727376b3da10c5fa86bd5209f8e