lacp: Require successful LACP negotiations when configured.

lacp: Require successful LACP negotiations when configured.

In the original Open vSwitch LACP implementation, when no slaves
found a LACP partner, the LACP module would attach all of them.
This allowed the LACP bond to fall back to a standard bond when
partnered with a non-LACP switch.  In practice, this has caused
confusion with marginal benefit, so this feature is removed with
this patch.

Signed-off-by: Ethan Jackson <ethan@nicira.com>