pathfinder isn't considering node interface `is_active()` state, so it can find a path that is down

[viniarck]

When I was reviewing the code and running some exploratory tests, I realized that when the graph is being built and adding a node, it's not considering the status of the interface, which leaves room to find a path that's down, and incorrectly returning it as a available path.

How to reproduce:

• Run mininet with this linear topology, sudo mn -c && sudo mn --controller=remote,ip=127.0.0.1,port=6653 --switch=ovsk,protocols=OpenFlow13 --topo=linear,3
• Shutdown a leaf node, like, sudo ifconfig s3-eth1 down
• Make a request /api/kytos/pathfinder/v2, trying to find a path terminating on this interface with this payload, notice the path will still be returned:

{
    "source": "00:00:00:00:00:00:00:01:1",
    "destination": "00:00:00:00:00:00:00:03:1"
}

response:

{
    "paths": [
        {
            "cost": 8,
            "hops": [
                "00:00:00:00:00:00:00:01:1",
                "00:00:00:00:00:00:00:01",
                "00:00:00:00:00:00:00:01:2",
                "00:00:00:00:00:00:00:02:2",
                "00:00:00:00:00:00:00:02",
                "00:00:00:00:00:00:00:02:3",
                "00:00:00:00:00:00:00:03:2",
                "00:00:00:00:00:00:00:03",
                "00:00:00:00:00:00:00:03:1"
            ]
        }
    ]
}