Adjust checker code to read json first with binary fallback.

Adjust the checker code used by CQ checkers to attempt to read the
config input as json first with a temporary fallback to binary. When the
binary is removed the fallback parsing can be removed.

BUG=chromium:1073530
TEST=./run_py_unittests.sh

Change-Id: I5976ff83291a5f59461dcac54f97fc936ff7aca9
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/config/+/2174612
Reviewed-by: Andrew Lamb <andrewlamb@chromium.org>
Commit-Queue: David Burger <dburger@chromium.org>
Tested-by: David Burger <dburger@chromium.org>
diff --git a/payload_utils/checker.py b/payload_utils/checker.py
index 6a04599..eaeff6c 100755
--- a/payload_utils/checker.py
+++ b/payload_utils/checker.py
@@ -20,15 +20,15 @@
       '--program',
       required=True,
       help=(
-          'Path to the program config binary proto e.g. '
-          '.../chromiumos/src/program/program1/generated/config.binaryproto.'),
+          'Path to the program config json proto e.g. '
+          '.../chromiumos/src/program/program1/generated/config.jsonproto.'),
       metavar='PATH')
   parser.add_argument(
       '--project',
       required=True,
       help=(
           'Path to the project config binary proto e.g. '
-          '.../chromiumos/src/project/project1/generated/config.binaryproto.'),
+          '.../chromiumos/src/project/project1/generated/config.jsonproto.'),
       metavar='PATH')
   return parser