Fix refcounting for sockets when stcb/inp kill timer fires.
Fix refcounting for sockets when stcb/inp kill timer fires.

Thanks to Anatoly Korniltsev for reporting issue #571.

CoolmanCZ/usrsctp,CoolmanCZ/usrsctp,sctplab/usrsctp,sctplab/usrsctp,weinrank/usrsctp,weinrank/usrsctp,weinrank/usrsctp,sctplab/usrsctp,CoolmanCZ/usrsctp,CoolmanCZ/usrsctp