Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Set TEST_DB_URL for storperf"
  - Set TEST_DB_URL for storperf

    JIRA: YARDSTICK-692

    add the URL for the test results DB to the storperd_admin-rc
    TEST_DB_URL=http://testresults.opnfv.org/test/api/v1
    Also, add metadata JSON to the POST to /job API when creating the job:

    Change-Id: Ib950f759d80e707bc49d9015bc120d985051f131
    Signed-off-by: JingLu5 <lvjing5@huawei.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 14bc98f..20b220b 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 14bc98f0e810e37f4600cb0b16d227e8290e1db2
+Subproject commit 20b220b4907b92b3b1afe659f532f3bb931d0c43