src/api2/admin/datastore/backup.rs: add speedtest api, improve upload speed

We need to disable tcp Nagle algorythm (set_nodelay), and use larger window size for http2

src/client/pipe_to_stream.rs

@@ -29,9 +29,9 @@ impl Future for PipeToSendStream {
     fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
         loop {
             if self.data != None {
-                // we don't have the next chunk of data yet, so just reserve 1 byte to make
-                // sure there's some capacity available. h2 will handle the capacity management
-                // for the actual body chunk.
+                // just reserve 1 byte to make sure there's some
+                // capacity available. h2 will handle the capacity
+                // management for the actual body chunk.
                 self.body_tx.reserve_capacity(1);
 
                 if self.body_tx.capacity() == 0 {