Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge changes from topics 'YARDSTICK-1218', 'YARDSTICK-1216', 'YARDSTICK-1215', 'YARDSTICK-1214'

    * changes:
      Move IncorrectConfig, IncorrectSetup and IncorrectNodeSetup to exceptions
      Move ErrorClass definition to exceptions module
      Convert SSH custom exceptions to Yardstick exceptions
      Remove AnsibleCommon class method mock

  - Move IncorrectConfig, IncorrectSetup and IncorrectNodeSetup to exceptions

    JIRA: YARDSTICK-1218

    Change-Id: I804065e9bce3e728f5bf9e756a78df8fd28f74ac
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>
  - Move ErrorClass definition to exceptions module

    JIRA: YARDSTICK-1216

    Change-Id: I82556e1d1b0c723221a58e188067cbce560b8338
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>
  - Convert SSH custom exceptions to Yardstick exceptions

    JIRA: YARDSTICK-1215

    Change-Id: I5ecfd3dccd91b07cd8de5309dfa1a372eff16ed0
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>
  - Remove AnsibleCommon class method mock

    In [1], several methods in "AnsibleCommon" class are mocked, but those
    mocks are not removed after the test execution. Depending on the test
    execution order, this affects other results.

    [1] https://github.com/opnfv/yardstick/blob/stable/fraser/yardstick/tests/unit/service/test_environment.py#L20

    JIRA: YARDSTICK-1214

    Change-Id: I85ef702b3b5b2fda5cf453a21b9f0bec61b155f0
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 98294f2..2cf8186 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 98294f2c8153f663c3b3a4e4cb98910e9d5cb602
+Subproject commit 2cf8186d9ccd6e5a51deffe87172fed8fe46c36b