DNSPolicy: Add routing strategy type conflict test

[mikenairn]

What

Add a test that checks the status of a DNSPolicy that has a conflicting strategy to an existing DNSPolicy with the same dnsName.

Steps:

1. Create Gateway 1 with listener foo -> foo.example.com
2. Create Gateway 2 with listener foo -> foo.example.com
3. Update status of gateway 1 to show attached routes for listener foo and address (127.0.0.1)
4. Update status of gateway 2 to show attached routes for listener foo and address (127.0.0.1)
5. Create DNSPolicy 1 targeting gateway 1 with a simple routing strategy
6. Verify DNSPolicy 1 becomes ready and the expected DNSRecord is created and ready
7. Create DNSPolicy 2 targeting gateway 2 with a loadbalanced routing strategy
8. Verify DNSPolicy 2 does not become ready and the expected DNSRecord is created but not ready and that both have the expected error:

record type conflict, cannot update endpoint 'foo.example.com' with record type 'CNAME' when endpoint already exists with record type 'A'

Note: Since this test will run in the kuadrant operator using a dns operator with default configurations for default and validation re-queue times it might not be possible to check much else without it taking too long.

Depends on #601