Update git submodules

* Update docs/submodules/releng from branch 'master'
  to 15110aa1c83e430cab86c342a3f85f6b64c892d3
  - Call system prune for podman too

    Change-Id: I02d283606f936978812ca6087d6b2091eab4392e
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index b572797..15110aa 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit b5727972e26ea4ca373c8d4452158ac596672343
+Subproject commit 15110aa1c83e430cab86c342a3f85f6b64c892d3