Update git submodules

* Update docs/submodules/releng from branch 'master'
  - CPERF: Do not remove docker images in clean

    Removing the cperf docker image in clean just adds more overhead to the
    next cperf run, because the entire docker image has to be re-downloaded.
    Docker pull will automatically download the difference between the old
    image and the new image (less bandwidth) so there is no reason to remove
    the image.

    Change-Id: I79ba2af20e3bdacfedc28d468fb629e040d7098f
    Signed-off-by: Tim Rozet <trozet@redhat.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 7502920..ba56b76 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 7502920ec103bc37abf4b7060957e55971b910d0
+Subproject commit ba56b767edab4fb35b486166e6bba00fee675ad6