snap maas init region with no arguments gives traceback

[Spencer Seidel]

This is with the stable and edge versions of the maas snap.

To reproduce:

$ sudo snap install maas --stable --devmode
maas 2.3.3-6498-ge4db91d-snap from Canonical✓ installed
$ sudo maas init --mode region
MAAS URL [default=http://192.168.1.12:5240/MAAS]:
Traceback (most recent call last):
  File "/snap/maas/2589/bin/maas", line 24, in <module>
    sys.exit(run())
  File "/snap/maas/2589/bin/maas", line 21, in run
    return maascli.main()
  File "/snap/maas/2589/lib/python3.5/site-packages/maascli/__init__.py", line 29, in main
    options.execute(options)
  File "/snap/maas/2589/lib/python3.5/site-packages/maascli/snappy.py", line 582, in __call__
    raise exc
  File "/snap/maas/2589/lib/python3.5/site-packages/maascli/snappy.py", line 579, in __call__
    self.handle(options)
  File "/snap/maas/2589/lib/python3.5/site-packages/maascli/snappy.py", line 679, in handle
    help_text=ARGUMENTS['database_host']['help'])
KeyError: 'database_host'