Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Perform a Mock tag

    tagging the sandbox project to verify release automation is working as
    intended.

    Change-Id: Iba5a8e8d612c9a7fb50db41cb5e46777901e70ad
    Signed-off-by: Aric Gardner <agardner@linuxfoundation.org>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 52d29ad..6d7a7ad 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 52d29ad095ad729a0287ec07a2c19072b4fb672b
+Subproject commit 6d7a7ad080d3612b80e761b439dbed91b8ae977b