Since the scheme of limiting the number of TCP slots to whatever will
fit in the current TCP window seems to be working well (Andy reports
getting within 20% of the 'iperf' send performance on a 10GigE link)
we should just let that be the default mode of operation.

Users may still set their own limits using the tcp_max_slot_table_entries
parameter if they need to.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>