Key was converted through str() even if None, resulting in "None" being

added to authorized_keys when no key was specified.

nova/virt/libvirt_conn.py

@@ -828,7 +828,10 @@ class LibvirtConnection(driver.ComputeDriver):
         if FLAGS.libvirt_type == 'lxc':
             target_partition = None
 
+        if inst['key_data']:
             key = str(inst['key_data'])
+        else:
+            key = None
         net = None
 
         nets = []