Bugfix in the wait-for-optional-LF logic

Any other character than LF after a CR means the end of the line
In sendFTPdata_low the delay must come after receiving +FTPPUT:2,num

There still seems to be need for a delay between +FTPPUT:2,num and actually
sending the bytes. Also the delays caused by printing diagnostic messages
seem to have an influence. It's puzzling.