Have the lagg interface generate link up/down events, the interface is marked as up if at least one of its ports also has a link up. This fixes using carp+lagg together and any other system that relies on linkstate events.
Have the lagg interface generate link up/down events, the interface is marked
as up if at least one of its ports also has a link up. This fixes using
carp+lagg together and any other system that relies on linkstate events.

PR:		kern/113956
MFC after:	3 days

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