Fix: check for TCP_CLOSE in mptcp_sub_force_close

No commments... How is it possible to write such a if statement...

Mea Culpa

Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
Fix: bug with data fin

This patch fixes issues when a data fin with or without data is followed by
subsequent data segments.

Signed-off-by: Gregory Detal <gregory.detal@uclouvain.be>
Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
Do not add an already received segment to the meta rcv queue

Signed-off-by: Gregory Detal <gregory.detal@uclouvain.be>
Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>