8011234: Performance regression with ftp protocol when uploading in image mode

[Alan Bateman]

This is a small patch to the legacy ftp client to fix a performance 
regression that seems to have crept in when this code was refactored in 
jdk7. When uploading in image/binary mode (the default or when 
specifying type=i) then the URLConnection's getOutputStream method no 
longer returns an OutputStream that delegates to a buffered stream. This 
means that writing to the output stream essentially delegates to the raw 
socket stream.

The proposed change is here. As it's a performance fix then I don't 
propose to add new tests to the jdk repo.

http://cr.openjdk.java.net/~alanb/8011234/webrev/

Thanks,

-Alan.