vswitchd: LACP switch lacp_status to bit mask.

vswitchd: LACP switch lacp_status to bit mask.

Much of the LACP status information attached to an interface is
moved from an enum to a bit mask in this commit.  The main reason
to do this is to allow a link to be concurrently expired and
defaulted.  With this commit, if a link enters an expired state,
but has never had its partner information update, it will properly
set the defaulted flag in its LACP messages.