Make ec2/cloud.py use get_instance_availability_zone() helper

Commit 488fcb4ad3 added a helper
for getting the AZ for a instance. This patch makes use of that
helper method.

This also removes the now unused get_availability_zone_by_host()
method from ec2utils and adds a reset_cache() call to the class
setup of CloudTestCase in test_cloud.py to reset the cache now
used between tests.

Change-Id: I2dd6a54fcc7cefe17816d0fb2875d8da0ec57eba

nova/api/ec2/cloud.py

@@ -1241,8 +1241,8 @@ class CloudController(object):
             self._format_instance_root_device_name(instance, i)
             self._format_instance_bdm(context, instance['uuid'],
                                       i['rootDeviceName'], i)
-            host = instance['host']
-            zone = ec2utils.get_availability_zone_by_host(host)
+            zone = availability_zones.get_instance_availability_zone(context,
+                                                                     instance)
             i['placement'] = {'availabilityZone': zone}
             if instance['reservation_id'] not in reservations:
                 r = {}

nova/api/ec2/ec2utils.py

@@ -19,7 +19,6 @@ import re
 
 from oslo.utils import timeutils
 
-from nova import availability_zones
 from nova import context
 from nova import exception
 from nova.i18n import _
@@ -174,11 +173,6 @@ def get_ip_info_for_instance(context, instance):
     return get_ip_info_for_instance_from_nw_info(nw_info)
 
 
-def get_availability_zone_by_host(host, conductor_api=None):
-    return availability_zones.get_host_availability_zone(
-        context.get_admin_context(), host, conductor_api)
-
-
 def id_to_ec2_id(instance_id, template='i-%08x'):
     """Convert an instance ID (int) to an ec2 ID (i-[base 16 number])."""
     return template % int(instance_id)

nova/tests/unit/api/ec2/test_cloud.py

@@ -34,6 +34,7 @@ from nova.api.ec2 import cloud
 from nova.api.ec2 import ec2utils
 from nova.api.ec2 import inst_state
 from nova.api.metadata import password
+from nova import availability_zones
 from nova.compute import api as compute_api
 from nova.compute import flavors
 from nova.compute import power_state
@@ -140,6 +141,7 @@ class CloudTestCase(test.TestCase):
         super(CloudTestCase, self).setUp()
         self.useFixture(test.SampleNetworks())
         ec2utils.reset_cache()
+        availability_zones.reset_cache()
         self.flags(compute_driver='nova.virt.fake.FakeDriver',
                    volume_api_class='nova.tests.unit.fake_volume.API')
         self.useFixture(fixtures.FakeLogger('boto'))