Leverage last_status metadata to notify only once

[viniarck]

Currently, certain notify_link_status_change calls are being refactored to always check the for the status property to make sure there aren't other protocol related features that might be resulting in protocol down. However, currently, there can be more than one notification, for instance:

If a link goes up, and then liveness goes up after that it could send a kytos/topology.link_up notification twice, so to solve this in a agnostic way without extra conditionals on multiple places we could leverage the last_status that will be delivered on issue #99, and then whenever a handler needs to send a notification it can check if the last_status for an entity is the same or not, in addition to checking the current status, so if the last_status is the same then no new notifications are needed.