Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Add API to update openrc variable

    JIRA: YARDSTICK-651

    Currently we source openrc variable manually or use yardstick env
    prepare to get openrc file.
    We need API to update the openrc variable.

    api: /yardstick/env/action
    description: source environment variable
    method: POST

    parameters:
    {
        'action': 'update_openrc',
        'args':{
            'openrc': {
                'OS_USERNAME': 'admin',
                'OS_PASSWORD': 'console',
                'OS_TENANT_NAME': 'admin',
                'OS_AUTH_URL': 'http://192.168.131.222:5000/v2.0',
                'EXTERNAL_NETWORK': 'ext-net'
            }
        }
    }

    Change-Id: I680a7249116c8ff0c1a9e7d5089538d935240c80
    Signed-off-by: chenjiankun <chenjiankun1@huawei.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 417df81..674a990 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 417df8187c1ddb04066409db6b2360b85c894b65
+Subproject commit 674a9902d40aef9a4c80669a0d00fc47447a806e