Configuring the DNS zone on a cluster with '.' as the last character, breaks DNS

[Andres Rodriguez]

THe Cluster Controller was configured with a DNS Zone as follows that contained a '.' at the end of the zone name:

'cluster.one.' instead of 'cluster.one'

when using the '.' at the end of the zone, we would see the following issue:

2015-03-18 13:53:03 [maas.dns] ERROR: Reloading BIND zone u'cluster.mallards.' failed: Command `rndc -c /etc/bind/maas/rndc.conf.maas reload cluster.mallards.` returned non-zero exit status 1:
rndc: 'reload' failed: empty label
2015-03-18 13:53:03 [HTTPChannel,26,127.0.0.1] 500 Error - /MAAS/api/1.0/nodes/node-761b65be-cd69-11e4-ae5d-001b21006d7f/
 Traceback (most recent call last):
   File "/usr/lib/python2.7/dist-packages/django/core/handlers/wsgi.py", line 206, in __call__
     response = self.get_response(request)
   File "/usr/lib/python2.7/dist-packages/maasserver/utils/views.py", line 124, in get_response
     response = get_response(request)
   File "/usr/lib/python2.7/dist-packages/maasserver/utils/views.py", line 105, in get_response
     return django_get_response(request)
   File "/usr/lib/python2.7/dist-packages/django/core/handlers/base.py", line 194, in get_response
     response = self.handle_uncaught_exception(request, resolver, sys.exc_info())
 --- <exception caught here> ---
   File "/usr/lib/python2.7/dist-packages/django/core/handlers/base.py", line 118, in get_response
     response = middleware_method(request, e)
   File "/usr/lib/python2.7/dist-packages/maasserver/middleware.py", line 240, in process_exception
     self.RETRY_AFTER_SERVICE_UNAVAILABLE)
 exceptions.AttributeError: 'APIErrorsMiddleware' object has no attribute 'RETRY_AFTER_SERVICE_UNAVAILABLE'

After removing the '.', things worked again.

MAAS should allow the inclusion of the last '.' and deal with it gracefully, as this is how domains are referred to.