Fix test_pool sorted list assertion failures

Some of the tests expect to be able to sort on the pool NS record priority. However, the rand_ns_records fake data generator can create NS records with equal priority which leads to undefined sort orders and ultimately invalid test failures.[2]
This patch makes sure the fake ns records created for tests never have equal priority values.

[2] https://zuul.opendev.org/t/openstack/build/69325d93f36042f390b4301cfadd3aa8/log/job-output.txt#21738

Change-Id: Ic04d1fe093dee54da64ccb238e9650ad5fc47eb8
1 file changed