[HACK] *ensure* all pending data is sent when using Socks5

The Session Host will send a *bye bye* signal to the client before it
closes the connection. Unfortunately the Socks5 ByteStreamSession just
call Socket.close() which will just deallocate the socket.

As it is OS (TCP stack) dependent what will be transmitted when the
SO_LINGER option is disabled this HACK will enable this option to ensure
that the network layer behave the same on all JVM.

Change-Id: I057be4787bffcbf371371dc8f7ec16f442efeac7
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1376
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>