Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "[Functest] Add argument in function run_tiers()"
  - [Functest] Add argument in function run_tiers()

    Replace single by double quotes, variables should
    be within double quotes.

    Change-Id: I5dae42178f5638689a8c46e03a01c12bd42b65e1
    Signed-off-by: Jose Lausuch <jalausuch@suse.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 88f0b85..6c84af5 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 88f0b856c18abca765a3d4a6da1f7849096b9b73
+Subproject commit 6c84af5a470c520e43973a0db010b62c35286724