pool: Increase TCP backlog for FTP mover

globus-url-copy doesn't appear to handle data channel
TCP rejects well. To reduce the risk we increase the
backlog to 128 (JDK default is 50).

Target: trunk
Require-notes: yes
Require-book: no
Acked-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>
Patch: http://rb.dcache.org/r/6588/