Because of the object-server's interaction with ssync sender's
X-Backend-Replication-Headers when a object (or fragment archive) is
pushed unmodified to another node it's ETag value is duped into the
recieving ends metadata as Etag. This interacts poorly with the
reconstructor's RebuildingECDiskFileStream which can not know ahead of
time the ETag of the fragment archive being rebuilt.
Don't send the Etag from the local source fragment archive being used as
the basis for the rebuilt fragent archive's metadata along to ssync.
Change-Id: Ie59ad93a67a7f439c9a84cd9cff31540f97f334a
52b102163e