Correct host_key setting in statemachine driver

The correct node attribute is 'host_keys' not 'keys'.

Change-Id: I82cb93572df5606f521dc26d700880e8433a8645

nodepool/driver/statemachine.py

@@ -165,7 +165,7 @@ class StateMachineNodeLauncher(stats.StatsReporter):
             if (self.state_machine.complete and self.keyscan_future
                 and self.keyscan_future.done()):
                 keys = self.keyscan_future.result()
-                node.keys = keys
+                node.host_keys = keys
                 self.log.debug(f"Node {node.id} is ready")
                 node.state = zk.READY
                 self.zk.storeNode(node)

nodepool/tests/unit/test_driver_azure.py

@@ -57,6 +57,7 @@ class TestDriverAzure(tests.DBTestCase):
         self.assertEqual(node.shell_type, 'sh')
         self.assertEqual(node.attributes,
                          {'key1': 'value1', 'key2': 'value2'})
+        self.assertEqual(node.host_keys, ['ssh-rsa FAKEKEY'])
 
     def test_azure_diskimage(self):
         configfile = self.setup_config(