Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Apex: Fixes unset var checks

    Var checks for unset required proper parameter expansion to avoid
    nounset.

    Change-Id: Ide5db47e2243c8aee0f97369bf3cd0673e7f4bd3
    Signed-off-by: Tim Rozet <trozet@redhat.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index b8a9d73..a3af06b 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit b8a9d735ba1c4b529664344954df1e33264d8d4d
+Subproject commit a3af06b28b81c6fc0de69c8a6186c2685f5609ce