Updated git submodules

Project: releng/builder master 7bcb9c78fbfe76d90527d269bc1721d233800676

Pin RS Public cloud images to known working

We're having issues with RS Public Cloud when building newer Cent OS
images. This patch pins the public cloud base image we build against to
the last known working one.

Jira: RELENG-118
Change-Id: Iad0ec2d3e312c22042c15973cab0eef58c61fe9c
Signed-off-by: Thanh Ha <thanh.ha@linuxfoundation.org>

diff --git a/docs/submodules/releng/builder b/docs/submodules/releng/builder
index 6dcbaae23a2599e5b0170c72983bbd2faafe4d12..7bcb9c78fbfe76d90527d269bc1721d233800676 160000 (submodule)
--- a/docs/submodules/releng/builder
+++ b/docs/submodules/releng/builder
@@ -1 +1 @@
-Subproject commit 6dcbaae23a2599e5b0170c72983bbd2faafe4d12
+Subproject commit 7bcb9c78fbfe76d90527d269bc1721d233800676