NFS4.1: Fix bug server don't reply the right fore_channel to client at create_session

At the latest kernel(2.6.37-rc1), server just initialize the forechannel
at init_forechannel_attrs, but don't reflect it to reply.

After initialize the session success, we should copy the forechannel info
to nfsd4_create_session struct.

Reviewed-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Mi Jinlong <mijinlong@cn.fujitsu.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>