if hostname not set, sudo warning make maas throw 500

[David Britton]

When editing the cluster details page, I got this:

http://paste.ubuntu.com/11780419/

2015-06-26 16:32:43 [HTTPChannel,0,127.0.0.1] 500 Error - /MAAS/clusters/cdd3ae50-8448-4f5d-95ab-6c4c7de2049c/interfaces/br0/edit/
        Traceback (most recent call last):
          File "/usr/lib/python2.7/dist-packages/twisted/web/wsgi.py", line 315, in run
            appIterator = self.application(self.environ, self.startResponse)
          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 213, in get_response
            response = get_response(request)
          File "/usr/lib/python2.7/dist-packages/maasserver/utils/views.py", line 202, in get_response
            request, get_resolver(None), sys.exc_info())
        --- <exception caught here> ---
          File "/usr/lib/python2.7/dist-packages/maasserver/utils/views.py", line 187, in get_response
            return django_get_response(request)
          File "/usr/lib/python2.7/dist-packages/maasserver/utils/orm.py", line 331, in __exit__
            self.fire()
          File "/usr/lib/python2.7/dist-packages/provisioningserver/utils/twisted.py", line 154, in wrapper
            return func(*args, **kwargs)
          File "/usr/lib/python2.7/dist-packages/maasserver/utils/async.py", line 180, in fire
            self._fire_in_reactor(hook).wait()
          File "/usr/lib/python2.7/dist-packages/crochet/_eventloop.py", line 219, in wait
            result.raiseException()
          File "<string>", line 2, in raiseException

        provisioningserver.rpc.exceptions.CannotConfigureDHCP: DHCPv4 server failed to stop: Unable to parse the output from upstart for service 'maas-dhcpd'.

maas@canonical-bootstrap:/$ sudo service maas-dhcpd status
sudo: unable to resolve host canonical-bootstrap
maas-dhcpd stop/waiting

Once I fixed up the 'unable to resolve host..." warning. things worked fine.