seq: Add some comments.

Signed-off-by: Ben Pfaff <blp@nicira.com>
band: Fix error in bond_choose_output_slave() function.

This commit fixes the error introduced by commit 4a1b8f30e59 (bond:
Stop using tags.). The error is caused by mistakenly returning 'slave'
where 'slave->aux' should be returned.

Signed-off-by: Alex Wang <alexw@nicira.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>