Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "prototypes: xci: Make CLEAN_DIB_IMAGES variable configurable"
  - prototypes: xci: Make CLEAN_DIB_IMAGES variable configurable

    The CLEAN_DIB_IMAGES variable determines whether the /httpboot
    or /tftpboot directories will be removed before running the xci-deploy
    script. This forces XCI to re-create the target OS images. We moved
    this variable from env-vars to user-vars since this is something that
    users normally want to tweak in their deployments.

    Change-Id: Ia48bd63979e3837aab7e47c906c2501e7c7dd0e1
    Signed-off-by: Markos Chandras <mchandras@suse.de>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index dd79812..e43f4a7 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit dd798122fca46b7d550f019f0d73b9044e083818
+Subproject commit e43f4a702cbf8c26a4a32827a3823a18c187d10b