An upload can be finished with a PUT with no body. If that happens,
we send an empty chunk to our backend, which can end up using
extra storage and potentially using multipart objects on object
storage servers when not strictly necessary.
Simplify this by checking to see if we are getting any data from the
client before we start our push to the backend.
Change-Id: Ia2069364ba2a5e03331f9eabca692b5aa065ce6e
7be52cae3a