test_external_dns: add missing test cases
Add NTP, ipa-ca and ADTrust system records tests. Also test if
changes are being reflected when uninstalling a host.
The test cases are added as extension into test_dns_locations suite.
https://pagure.io/freeipa/issue/6091
Reviewed-By: Martin Basti <mbasti@redhat.com>
Reviewed-By: Tomas Krizek <tkrizek@redhat.com>