pformat: convert various json dump logic to new helper

This makes the output consistent for humans & compact.

BUG=None
TEST=unittests pass

Change-Id: Ic2652095fdbe023caf2af11260c50d59bcbc5f0e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2237071
Reviewed-by: Chris McDonald <cjmcdonald@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/cbuildbot_launch_unittest.py b/scripts/cbuildbot_launch_unittest.py
index bff8973..bf8722b 100644
--- a/scripts/cbuildbot_launch_unittest.py
+++ b/scripts/cbuildbot_launch_unittest.py
@@ -288,9 +288,9 @@
             '--master-build-id', '123456789',
             '--buildnumber', '314',
             '--previous-build-state',
-            'eyJicmFuY2giOiAiYnJhbmNoIiwgImJ1aWxkX251bWJlciI6IDMxMywgImJ1aWx'
-            'kcm9vdF9sYXlvdXQiOiAyLCAibWFzdGVyX2J1aWxkX2lkIjogMTIzMTIzMTIzLC'
-            'Aic3RhdHVzIjogImZhaWwifQ==',
+            'eyJicmFuY2giOiJicmFuY2giLCJidWlsZF9udW1iZXIiOjMxMywiYnVpbGRyb290X'
+            '2xheW91dCI6MiwibWFzdGVyX2J1aWxkX2lkIjoxMjMxMjMxMjMsInN0YXR1cyI6Im'
+            'ZhaWwifQ==',
             '--workspace', '/root/workspace',
             '--cache-dir', '/cache',
         ],