Fix potential hash mismatch on tracker-file-resumed download + fp.tell()
Fix potential hash mismatch on tracker-file-resumed download + fp.tell()

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