500 error on 'nova host-update --status [enabled|disabled] when using xenapi aggregates'

Root cause is that the xenhost operation gets confused when executed in resource pools.

I thought I caught all cases, but clearly I didn't :(

Stacktrace is here:

nova-compute WARNING Task [Async.host.call_plugin] OpaqueRef:ec4b25a7-3e53-f7e1-c377-325c786bb29f status: failure ['XENAPI_PLUGIN_FAILURE', 'set_host_enabled', 'PluginError ', 'Error: Multiple matching hosts found. --multiple required to complete the operation\n']
nova-compute ERROR The call to set_host_enabled returned an error: ['XENAPI_PLUGIN_FAILURE', 'set_host_enabled', 'PluginError', 'Error: Multiple matching hosts found. --multip le required to complete the operation\n'].
nova-compute ERROR Exception during message handling
(nova.rpc): TRACE: Traceback (most recent call last):
(nova.rpc): TRACE: File "/usr/lib/python2.6/site-packages/nova/rpc/amqp.py", line 249, in _process_data
(nova.rpc): TRACE: rval = node_func(context=ctxt, **node_args)
(nova.rpc): TRACE: File "/usr/lib/python2.6/site-packages/nova/exception.py", line 126, in wrapped
(nova.rpc): TRACE: return f(*args, **kw)
(nova.rpc): TRACE: File "/usr/lib/python2.6/site-packages/nova/compute/manager.py", line 1424, in set_host_enabled
(nova.rpc): TRACE: return self.driver.set_host_enabled(host, enabled)
(nova.rpc): TRACE: File "/usr/lib/python2.6/site-packages/nova/virt/xenapi_conn.py", line 530, in set_host_enabled
(nova.rpc): TRACE: return self._host.set_host_enabled(host, enabled)
(nova.rpc): TRACE: File "/usr/lib/python2.6/site-packages/nova/virt/xenapi/host.py", line 98, in set_host_enabled
(nova.rpc): TRACE: return response.get("status", response)
(nova.rpc): TRACE: AttributeError: 'str' object has no attribute 'get'
(nova.rpc): TRACE:
nova-compute ERROR Returning exception 'str' object has no attribute 'get' to caller