Unity: fail to detach lun when auto zone enabled

When the lun is the last one attached to the host and it is detached,
the attribute `host.host_luns` is None. Use `not` in if statement which
is pythonic in checking None and empty list of `host.host_luns`.

Change-Id: I5d8f63f9a78d001bc699af538f586aab8d73a5cf
Closes-bug: #1759175

cinder/tests/unit/volume/drivers/dell_emc/unity/test_adapter.py

@@ -795,6 +795,19 @@ class FCAdapterTest(test.TestCase):
         target_wwn = ['100000051e55a100', '100000051e55a121']
         self.assertListEqual(target_wwn, data['target_wwn'])
 
+    def test_terminate_connection_auto_zone_enabled_none_host_luns(self):
+        connector = {'host': 'host-no-host_luns', 'wwpns': 'abcdefg'}
+        volume = MockOSResource(provider_location='id^lun_41', id='id_41')
+        ret = self.adapter.terminate_connection(volume, connector)
+        self.assertEqual('fibre_channel', ret['driver_volume_type'])
+        data = ret['data']
+        target_map = {
+            '200000051e55a100': ('100000051e55a100', '100000051e55a121'),
+            '200000051e55a121': ('100000051e55a100', '100000051e55a121')}
+        self.assertDictEqual(target_map, data['initiator_target_map'])
+        target_wwn = ['100000051e55a100', '100000051e55a121']
+        self.assertListEqual(target_wwn, data['target_wwn'])
+
     def test_validate_ports_whitelist_none(self):
         ports = self.adapter.validate_ports(None)
         self.assertEqual(set(('spa_iom_0_fc0', 'spa_iom_0_fc1')), set(ports))

cinder/tests/unit/volume/drivers/dell_emc/unity/test_client.py

@@ -161,6 +161,8 @@ class MockResource(object):
 
     @property
     def host_luns(self):
+        if self.name == 'host-no-host_luns':
+            return None
         return []
 
     @property

cinder/volume/drivers/dell_emc/unity/adapter.py

@@ -755,7 +755,7 @@ class FCAdapter(CommonAdapter):
                 'data': {}
             }
             host = self.client.create_host(connector['host'])
-            if len(host.host_luns) == 0:
+            if not host.host_luns:
                 targets = self.client.get_fc_target_info(
                     logged_in_only=True, allowed_ports=self.allowed_ports)
                 ret['data'] = self._get_fc_zone_info(connector['wwpns'],

releasenotes/notes/fail-detach-lun-when-auto-zone-enabled-9c87b18a3acac9d1.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    Dell EMC Unity Driver: Fixes `bug 1759175
+    <https://bugs.launchpad.net/cinder/+bug/1759175>`__
+    to detach the lun correctly when auto zone was enabled and the lun was the
+    last one attached to the host.