Update git submodules

* Update docs/submodules/releng from branch 'master'
  - [yardstick] Pass "BRANCH" variable to yardstick docekr container

    Recently update of utils/fetch_os_creds.sh in commit 8359219bae93a028f6205cdc9460654f9e45c217
    use a "BRANCH" varibale in fuel environmet
    Currently Yardstick didn't pass such variable to yardstick docker, which causes the following error:
    /home/opnfv/repos/releng/utils/fetch_os_creds.sh: line 75: BRANCH: unbound variable

    This patch fix this error by Pass "BRANCH" variable to yardstick docekr container

    Change-Id: Ifcf3df7107b2f4b493b37c7ef5473f170a8edb94
    Signed-off-by: JingLu5 <lvjing5@huawei.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index cebfb87..eec4eff 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit cebfb874b5d9e759f9d97f8eee9d1d0a2dfab8ce
+Subproject commit eec4effc7f71c89549cbf90d9c140ce0b473555d