Fix test suite to use MiniDNS

MiniDNS changes:

* In create_entry/delete_entry, if we don't get a name
then we throw an exception

* In get_entries_by_address, filter out duplicates

* Add a log.warn in addition to throwing an exception.

Test Suite changes:

* Updates base TestCase to use MiniDNS instead of the default DNSDriver.

* Make sure we cleanup the dnstest.txt and the temporary directory
  in TestCase.tearDown()

* Update a few tests to pass in display_name

Fixes LP Bug #1081750

Change-Id: Ia8d80102deaeaaac166ab50bbd47279d72d1e389

nova/tests/fake_flags.py

@@ -45,3 +45,5 @@ def set_defaults(conf):
     conf.set_default('rpc_response_timeout', 5)
     conf.set_default('rpc_cast_timeout', 5)
     conf.set_default('lock_path', None)
+    conf.set_default('floating_ip_dns_manager', 'nova.tests.utils.dns_manager')
+    conf.set_default('instance_dns_manager', 'nova.tests.utils.dns_manager')

nova/tests/test_xenapi.py

@@ -982,6 +982,7 @@ class XenAPIVMTestCase(stubs.XenAPITestBase):
         instance_values = {
             'id': instance_id,
             'uuid': '00000000-0000-0000-0000-00000000000%d' % instance_id,
+            'display_name': 'host-%d' % instance_id,
             'project_id': self.project_id,
             'user_id': self.user_id,
             'image_ref': 1,