Shouldn't generate linkState alerts for intentionally shutdown interfaces

[Morten Brekkevold]

When ipdevpoll generates alerts for link state changes, it only considers changes in an interface's operStatus. When a link is intentionally taken down (i.e. the interface is shutdown by an operator), both the adminStatus and the operStatus change.

If the adminStatus is down, the operStatus change is a result of that, and the link loss was likely intentional - i.e. NAV shouldn't generate an alert in that case.

The linkstate trap plugin should also be reviewed to see how linkstate traps are handled in this regard.

[Morten Brekkevold (mbrekkevold)]

fix here: https://nav.uninett.no/hg/stable/rev/a1fa214856ab