Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Add task-args(from yaml file) candidates in /api/v2/yardstick/testcases API"
  - Add task-args(from yaml file) candidates in /api/v2/yardstick/testcases API

    JIRA: YARDSTICK-766

    We have the demand to get all task-args candidates in test case yaml
    file,
    so that user get easily change it.
    The response will like:
    {
        'status': 1,
        'result': {
            'testcase': case content,
            'args': {
                'image': {'description': '', 'type': 'String'}
            }
        }
    }

    In this patch, I add jinja2schema 0.1.4 in requirements.txt.

    Change-Id: I450082402370add5ab29090286f026fe3cc8c36e
    Signed-off-by: chenjiankun <chenjiankun1@huawei.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index b57da14..e78324b 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit b57da1432fae39ea414c42734e730df329de66e3
+Subproject commit e78324bf2672a694f460e953373f18729c476e8d