Upgrading to MAAS 1.7.1 to 1.7.2 causes migrations to fail

[Andres Rodriguez]

> django.contrib.staticfiles
 > piston
 > south

Not synced (use migrations):
 - maasserver
 - metadataserver
(use ./manage.py migrate to migrate these)
Traceback (most recent call last):
  File "/usr/sbin/maas-region-admin", line 16, in <module>
    management.execute_from_command_line()
  File "/usr/lib/python2.7/dist-packages/django/core/management/__init__.py", line 399, in execute_from_command_line
    utility.execute()
  File "/usr/lib/python2.7/dist-packages/django/core/management/__init__.py", line 392, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/lib/python2.7/dist-packages/django/core/management/base.py", line 242, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/usr/lib/python2.7/dist-packages/django/core/management/base.py", line 285, in execute
    output = self.handle(*args, **options)
  File "/usr/lib/python2.7/dist-packages/south/management/commands/migrate.py", line 107, in handle
    ignore_ghosts = ignore_ghosts,
  File "/usr/lib/python2.7/dist-packages/south/migration/__init__.py", line 199, in migrate_app
    applied_all = check_migration_histories(applied_all, delete_ghosts, ignore_ghosts)
  File "/usr/lib/python2.7/dist-packages/south/migration/__init__.py", line 88, in check_migration_histories
    raise exceptions.GhostMigrations(ghosts)
south.exceptions.GhostMigrations:

 ! These migrations are in the database but not on disk:
    <maasserver: 0115_unique_boot_source_selections>
    <maasserver: 0116_unique_boot_source_selections>
    <maasserver: 0117_delete_duplicate_config>
    <maasserver: 0118_config_key_unique>
    <maasserver: 0119_migrate_invalid_network_names>
    <maasserver: 0120_make_macaddress_node_nullable>
 ! I'm not trusting myself; either fix this yourself by fiddling
 ! with the south_migrationhistory table, or pass --delete-ghost-migrations
 ! to South to have it delete ALL of these records (this may not be good).

To reproduce:
1. sudo add-apt-repository ppa:maas-maintainers/stable
2. sudo apt-get update && sudo apt-get install maas
3. sudo maas-region-admin createadmin
4. sudo add-apt-repository ppa:maas-maintainers/testing
5. sudo apt-get update && sudo apt-get dist-upgrade.