network: introduce 'degraded-carrier' operstate to order all states

network: introduce 'degraded-carrier' operstate to order all states

Previously, 'degraded' state is ambiguous for bonding or bridge master:
1. one or more slave interfaces does not have carrier,
2. no link local address is assigned to the master,
3. combination of the above two.

This makes the above case 1 and 3 are in the new 'degraded-carrier'
state, and makes 'degraded' state as all slaves are active but no
link local address on master.