Update git submodules

* Update docs/submodules/releng/builder from branch 'master'
  to 79b09ce26f835071b813f35a17190327d12271b6
  - Improve Stack cleanup to check on each delete

    There is a race condition between when we query Jenkins for a list
    of in use builds to compare with stacks and when they are actually
    deleted. Shorten that race condition by querying on every stack
    check.

    Hopefully this will reduce the chance that Jenkins deletes a stack
    that is in progress building and has not yet attached to Jenkins.

    Issue: RELENG-75
    Change-Id: I2fcc0a9bef34708062e69f4d8a4ee04dfd6108b5
    Signed-off-by: Thanh Ha <thanh.ha@linuxfoundation.org>
  - Remove unnecessary echo

    `openstack stack show` already prints to the screen so it does not
    really make sense to store it in a variable and echo it again.

    Change-Id: Idfbfae0b686867044b6fe4981156dac18cc4c3a4
    Signed-off-by: Thanh Ha <thanh.ha@linuxfoundation.org>

diff --git a/docs/submodules/releng/builder b/docs/submodules/releng/builder
index cc4af86710354d2671e9151b6525b3b9595bea23..79b09ce26f835071b813f35a17190327d12271b6 160000 (submodule)
--- a/docs/submodules/releng/builder
+++ b/docs/submodules/releng/builder
@@ -1 +1 @@
-Subproject commit cc4af86710354d2671e9151b6525b3b9595bea23
+Subproject commit 79b09ce26f835071b813f35a17190327d12271b6