Update common-packer to v0.7.1

This fix is needed to resume packer builds, which are currently
broken.

Issue: LF-Jira RELENG-3344
Change-Id: I490c3d0ef8c59ae981232de0edc5dcaf13238b26
Signed-off-by: Eric Ball <eball@linuxfoundation.org>

diff --git a/packer/common-packer b/packer/common-packer
index e96974f..6485404 160000 (submodule)
--- a/packer/common-packer
+++ b/packer/common-packer
@@ -1 +1 @@
-Subproject commit e96974fa52edb7d8e7f27d314155bd088255e07d
+Subproject commit 6485404dda02505f48cef60d9aafd726c3aacfa8