Clarify du behavior for file/object hierarchies
Clarify du behavior for file/object hierarchies

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BrandonY/gsutil,craigcitro/gsutil,mattdr/gsutil,dtjackson/gsutil,dimfeld/gsutil,chriskuehl/gsutil-debian,GoogleCloudPlatform/gsutil,GoogleCloudPlatform/gsutil,fishjord/gsutil,ttiurani/gsutil