Update git submodules

* Update docs/submodules/releng from branch 'master'
  to 747df971c7996c7c6f5cb2721ba01bf4e8085617
  - Update Jerma branch for Airship Installer

    Update with correct branch name and sh

    Signed-off-by: James Gu <james.gu@att.com>
    Change-Id: Ib9a553e420cd69d569d9678d265efc9feb6fed20

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 5f71cc3..747df97 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 5f71cc38f91f9dc5bf8404af542be5017d57ab85
+Subproject commit 747df971c7996c7c6f5cb2721ba01bf4e8085617