Inconsistent display of IP family on aggregate API serializer

[jeremystretch]

Environment

• Python version: 3.6.8
• NetBox version: 2.6.12

Steps to Reproduce

1. Request a prefix object via the REST API
2. Request an aggregate object via the REST API

Expected Behavior

The family field for both objects should have the same format.

Observed Behavior

The prefix serializer renders family using a choice dictionary:

    "family": {
        "value": 4,
        "label": "IPv4"
    },

However, the aggregate serializer does not:

    "family": 4,

AggregateSerializer should be corrected to display the IP address family in the same manner as the prefix and IP address serializers.