Update git submodules

* Update docs/submodules/releng from branch 'master'
  to b7871b1916fc8941c39950a9fb05308432a3a065
  - use `bash` to parse shell

    Test runs failed because of no `source` command can be found.
    See: https://build.opnfv.org/ci/job/doctor-verify-fault_management-fuel-sample-x86_64-master/45/console

    Change-Id: I05cdcaec6e0a7289f92ad49e7abd35c3c848a877
    Signed-off-by: dongwenjuan <dong.wenjuan@zte.com.cn>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 16ee0f2..b7871b1 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 16ee0f28ee0ad12b3f074bc09076a3ecf6e52844
+Subproject commit b7871b1916fc8941c39950a9fb05308432a3a065