CheckDirMetadataFormat: LocalPath() -> AbsoluteLocalPath()

LocalPath() should be used in error messages, but never when actually
trying to access a path.

Bug: 1127507
Change-Id: I03ec5421891ac67a8620cd3c7e88c2de1811e914
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2418914Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>
Auto-Submit: Andrew Grieve <agrieve@chromium.org>

presubmit_canned_checks.py

@@ -1051,7 +1051,7 @@ def CheckDirMetadataFormat(input_api, output_api, dirmd_bin=None):
   file_filter = lambda f: (
       input_api.basename(f.LocalPath()) in ('DIR_METADATA', 'OWNERS'))
   affected_files = set([
-      f.LocalPath()
+      f.AbsoluteLocalPath()
       for f in input_api.change.AffectedFiles(
           include_deletes=False, file_filter=file_filter)
   ])