Textual evaluation filters don't work for IP fields

[jeremystretch]

Issue type

[ ] Feature request
[x] Bug report
[ ] Documentation

Environment

• Python version: 3.4.3
• NetBox version: 2.2.2

Description

Text-based search filters (startswith, endswith, regex, and their case-insensitive counterparts) are not properly evaluated for IPNetworkFields and IPAddressFields:

>>> from netaddr import IPNetwork
>>> IPAddress(address=IPNetwork('192.0.2.1/24')).save()
>>> IPAddress(address=IPNetwork('192.0.2.2/24')).save()
>>> IPAddress(address=IPNetwork('192.0.2.3/24')).save()
>>> IPAddress.objects.filter(address__startswith='192.0.2')
<QuerySet []>