When the skb was shared with Ethereal, Ethereal was sometimes the last
user and the destructor would get called on another CPU, not
knowing anything about our sock_lock.  Move our rwnd updates and I/O 
redrive out of the skb destructor.

Also, if unable to allocate an skb for our transmission packet,
walk the packet's chunks and free the control chunks.  

Also change list_dels to list_del_init.  Fix real later, but this prevent
us from a doing damage if we list_del twice.