Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "[Functest] Wget download_images.sh to support Alpine on Danube jobs"
  - [Functest] Wget download_images.sh to support Alpine on Danube jobs

    Change-Id: I70cf598a09def6c62dd4c32ed819e818833a6ff2
    Signed-off-by: jose.lausuch <jose.lausuch@ericsson.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 20826c0..12e8b5c 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 20826c00015567244153ab2e7b39452600fd38c7
+Subproject commit 12e8b5c1a72d7a29af8a356fed87373701221b2c