Enhance IPAdresses migration tests

This enhances IPAddresses tests to check if the migration goes fine with longer
IPv6, and with ipv6 that can be shortened (postgresql uses shortened form,
mysql and sqlite doesn't).

Also enhances cidr tests to check migration of shortenables cidrs, and cidrs
that postgresql suppress its prefix, like 10.0.0.0/32 cause it is pretty much
the same as 10.0.0.0

Partially implements bp migration-testing-with-data

Change-Id: I11dfc8fda7034a46a6bc067294ac8e88ca43b508
Merge "Enhance IPAdresses migration tests"