upload: don't return NotReady

We need to kick (poll) the stream's next element, so simply
reiterate, the try_read!() will then return NotReady from
the next stream item for us.

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>

src/api3/admin/datastore/upload_catar.rs

@@ -29,7 +29,6 @@ impl Future for UploadCaTar {
                     if let Err(err) = self.index.write(&chunk) {
                         bail!("writing chunk failed - {}", err);
                     }
-                    return Ok(Async::NotReady);
                 }
                 None => {
                     self.index.close()?;