Use fetch_artifact in _sync_artifact_as_log
Use fetch_artifact in _sync_artifact_as_log

Summary: Pretty much pure deduplication; one fewer place where we manually construct urls.

Test Plan: Unit

Reviewers: mkedia

Reviewed By: mkedia

Subscribers: changesbot, mkedia, wwu

Differential Revision: https://tails.corp.dropbox.com/D106548

wfxiang08/changes,bowlofstew/changes,wfxiang08/changes,dropbox/changes,wfxiang08/changes,bowlofstew/changes,wfxiang08/changes,dropbox/changes,dropbox/changes,bowlofstew/changes,dropbox/changes,bowlofstew/changes