Sockets aren't currently removed from the the global list when
they are destroyed. In addition, offload handlers need to be cleaned
up as well.

Fixes: 0b5e8b8e ("net: Add Geneve tunneling protocol driver")
CC: Andy Zhou <azhou@nicira.com>
Signed-off-by: Jesse Gross <jesse@nicira.com>
Acked-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>