(bug 68343) Links in first post weren't registered

Code attempted to fetch workflow from storage, but postrevision is actually
stored first, so at that point, workflow is not yet in storage.

Workflow was already being passed in $metadata, so we can just grab it there.

Bug: 68343
Change-Id: I941e1bd7d993fae9ae76af945ae2e62e1970c03b