Sec 3.1 Carrier delay, directly reference oper-status leaf

[rgwilton]

WG Last Call: draft-ietf-netmod-intf-ext-yang-07: Vladimir issue 2.

In sec "3.1 Carrier delay" use of the under-defined "Carrier"
definition can be replaced with direct reference to the oper-status leaf (which is what is actually targeted by the algorithm) "Operational status transition debouncing".

[samans]

Change carrier-delay to link-flap-suppression

[rgwilton]

I've just added a couple of further tweaks. It would be worth checking these.

I did wonder whether the YANG module descriptions should be tightened up to reference the oper-status leaf but decided not to change them in the end.