Wait for acks from the server when uploading.
Wait for acks from the server when uploading.

This removes a race in the server tests when testing uploads. However,
there is still a race when the upload is truncated because the server
doesn't ack those and the test doesn't know when the server has finished
writing the partial upload to disk.

sillvan/pond,ioerror/pond,saltthefries/pond,berkus/pond,sillvan/pond,infinity0/pond,berkus/pond,agl/pond,ArneBab/pond,ioerror/pond,infinity0/pond,agl/pond,saltthefries/pond,ArneBab/pond