bisect-kit: fix bisection range

If the two ends of bisection range are snapshot versions, the candidate
indexes may be wrong.

BUG=None
TEST=manually

Change-Id: Ie1a894ed3b4bc0d6fe4aa4b367ca28f838936180
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/bisect-kit/+/3205500
Tested-by: Kuang-che Wu <kcwu@chromium.org>
Auto-Submit: Kuang-che Wu <kcwu@chromium.org>
Commit-Queue: Zheng-Jie Chang <zjchang@chromium.org>
Reviewed-by: Zheng-Jie Chang <zjchang@chromium.org>
diff --git a/bisect_cros_version.py b/bisect_cros_version.py
index 838f85f..edb9627 100755
--- a/bisect_cros_version.py
+++ b/bisect_cros_version.py
@@ -39,7 +39,10 @@
   logger.info('use_snapshot: %s', use_snapshot)
   full_versions, details = cros_util.list_chromeos_prebuilt_versions(
       board, old, new, use_snapshot=use_snapshot)
-  short_versions = [cros_util.version_to_short(v) for v in full_versions]
+  short_versions = [
+      v if cros_util.is_cros_snapshot_version(v) else
+      cros_util.version_to_short(v) for v in full_versions
+  ]
 
   if cros_util.is_cros_snapshot_version(old):
     old_idx = full_versions.index(old)