Trim down primary_path and backup_path

[Alopalao]

primary_path and backup_path are treated as Path objects.
So they will have extra fields that are not necessary. This is the whole object in the DB:

    primary_path: [
      {
        id: 'c8b55359990f89a5849813dc348d30e9e1f991bad1dcb7f82112bd35429d9b07',
        endpoint_a: {
          id: '00:00:00:00:00:00:00:01:4',
          name: 's1-eth4',
          port_number: 4,
          mac: '76:ca:15:dd:21:42',
          switch: '00:00:00:00:00:00:00:01',
          type: 'interface',
          nni: true,
          uni: false,
          speed: 1250000000,
          metadata: {},
          lldp: true,
          active: true,
          enabled: true,
          status: 'UP',
          status_reason: [],
          link: 'c8b55359990f89a5849813dc348d30e9e1f991bad1dcb7f82112bd35429d9b07'
        },
        endpoint_b: {
          id: '00:00:00:00:00:00:00:03:3',
          name: 's3-eth3',
          port_number: 3,
          mac: '66:7b:b8:f6:da:6a',
          switch: '00:00:00:00:00:00:00:03',
          type: 'interface',
          nni: true,
          uni: false,
          speed: 1250000000,
          metadata: {},
          lldp: true,
          active: true,
          enabled: true,
          status: 'UP',
          status_reason: [],
          link: 'c8b55359990f89a5849813dc348d30e9e1f991bad1dcb7f82112bd35429d9b07'
        },
        metadata: { s_vlan: { tag_type: 'vlan', value: 1 } },
        active: true,
        enabled: true,
        status: 'UP',
        status_reason: []
      },
      {
        id: '4d42dc0852278accac7d9df15418f6d921db160b13d674029a87cef1b5f67f30',
        endpoint_a: {
          id: '00:00:00:00:00:00:00:02:3',
          name: 's2-eth3',
          port_number: 3,
          mac: 'ee:04:9b:22:d3:d4',
          switch: '00:00:00:00:00:00:00:02',
          type: 'interface',
          nni: true,
          uni: false,
          speed: 1250000000,
          metadata: {},
          lldp: true,
          active: true,
          enabled: true,
          status: 'UP',
          status_reason: [],
          link: '4d42dc0852278accac7d9df15418f6d921db160b13d674029a87cef1b5f67f30'
        },
        endpoint_b: {
          id: '00:00:00:00:00:00:00:03:2',
          name: 's3-eth2',
          port_number: 2,
          mac: '52:a2:6a:bd:28:4c',
          switch: '00:00:00:00:00:00:00:03',
          type: 'interface',
          nni: true,
          uni: false,
          speed: 1250000000,
          metadata: {},
          lldp: true,
          active: true,
          enabled: true,
          status: 'UP',
          status_reason: [],
          link: '4d42dc0852278accac7d9df15418f6d921db160b13d674029a87cef1b5f67f30'
        },
        metadata: { s_vlan: { tag_type: 'vlan', value: 1 } },
        active: true,
        enabled: true,
        status: 'UP',
        status_reason: []
      }
    ],

For example metadata is not necessary and caused some past errors.
For an EVC to have a working primary_path only the id of the endpoints are needed:

    "primary_path": [
     {"endpoint_a": {"id": "00:00:00:00:00:00:00:01:4"},
      "endpoint_b": {"id": "00:00:00:00:00:00:00:03:3"}},
     {"endpoint_a": {"id": "00:00:00:00:00:00:00:02:3"},
      "endpoint_b": {"id": "00:00:00:00:00:00:00:03:2"}}
    ]