Update the TopologyMetrics module to listen for all topology-related events:
Devices, Hosts, Links, TopologyEvent

Now the semantics for updating the metrics are:
 * Any topology-related event (DeviceEvent, HostEvent, LinkEvent,
   TopologyEvent) will update the Lost Topology Event Timestamp
 * Only the DeviceEvent, HostEvent and LinkEvent will be counted in
   measuring the event rate; TopologyEvent is excluded, because it
   is generated as a result of some of those events

Also, increased the number of saved events from 10 to 100.

Change-Id: Ie759ee69869cddc617d7ad5b8b75a622e2571620
3 files changed