[2.4b3] Error updating controller config

[Mark Shuttleworth]

Am working with controllers in MAAS and seeing unexpected behaviours. Also observed this in regiond.log not sure how it is related to what I am seeing:

2018-05-06 12:12:56 maasserver: [error] Error while calling DescribePowerTypes: RPC connection timed out to rack controller 'lapsi' (4nqs36).
2018-05-06 12:12:56 maasserver.websockets.protocol: [critical] Error on request (21) controller.update: 'tags'
 Traceback (most recent call last):
   File "/usr/lib/python3.6/threading.py", line 864, in run
     self._target(*self._args, **self._kwargs)
   File "/usr/lib/python3/dist-packages/provisioningserver/utils/twisted.py", line 850, in worker
     return target()
   File "/usr/lib/python3/dist-packages/twisted/_threads/_threadworker.py", line 46, in work
     task()
   File "/usr/lib/python3/dist-packages/twisted/_threads/_team.py", line 190, in doWork
     task()
 --- <exception caught here> ---
   File "/usr/lib/python3/dist-packages/twisted/python/threadpool.py", line 250, in inContext
     result = inContext.theWork()
   File "/usr/lib/python3/dist-packages/twisted/python/threadpool.py", line 266, in <lambda>
     inContext.theWork = lambda: context.call(ctx, func, *args, **kw)
   File "/usr/lib/python3/dist-packages/twisted/python/context.py", line 122, in callWithContext
     return self.currentContext().callWithContext(ctx, func, *args, **kw)
   File "/usr/lib/python3/dist-packages/twisted/python/context.py", line 85, in callWithContext
     return func(*args,**kw)
   File "/usr/lib/python3/dist-packages/provisioningserver/utils/twisted.py", line 883, in callInContext
     return func(*args, **kwargs)
   File "/usr/lib/python3/dist-packages/provisioningserver/utils/twisted.py", line 232, in wrapper
     result = func(*args, **kwargs)
   File "/usr/lib/python3/dist-packages/maasserver/utils/orm.py", line 756, in call_within_transaction
     return func_outside_txn(*args, **kwargs)
   File "/usr/lib/python3/dist-packages/maasserver/utils/orm.py", line 563, in retrier
     return func(*args, **kwargs)
   File "/usr/lib/python3.6/contextlib.py", line 52, in inner
     return func(*args, **kwds)
   File "/usr/lib/python3/dist-packages/maasserver/websockets/handlers/machine.py", line 361, in update
     self.update_tags(node_obj, params['tags'])
 builtins.KeyError: 'tags'