Comment 5 for bug 1378732

Dropping self.define_ml2_tables(metadata) it self for Juno won't work because we will find another error:

Traceback (most recent call last):
  File "migrate_to_ml2.py", line 485, in <module>
    main()
  File "migrate_to_ml2.py", line 481, in main
    args.vxlan_udp_port)
  File "migrate_to_ml2.py", line 142, in __call__
    self.migrate_network_segments(engine, metadata)
  File "migrate_to_ml2.py", line 163, in migrate_network_segments
    ml2_network_segments = metadata.tables['ml2_network_segments']
KeyError: 'ml2_network_segments'

metadata object won't have ml2_network_segments table if not executing define_ml2_tables.