Incomplete topology information causes eventengine to post boxShadow alerts instead of boxDown alerts

[Morten Brekkevold]

In cases where NAV's topology information is incomplete, the eventengine may misbehave when handling boxState events from pping.

Normally, eventengine uses topology information to detect the path between itself and the netbox that stopped responding to ping. Only paths where all nodes are up are considered. If no path is found, it is assumed that the target netbox is in shadow, and the event is translated into a boxShadow alert.

Unfortunately, when there is incomplete topology information, there may not be any path even when down-nodes are included, causing the same interpretation.

eventengine should verify that there is any path at all between nodes before excluding nodes that are down. If there isn't, eventengine should default to boxDown, since it cannot possibly know the shadow state.

[Morten Brekkevold (mbrekkevold)]

fix here: https://nav.uninett.no/hg/nav/rev/3139ed876f28