Allow gateway update when an user owns a gateway

[iychoi]

This fixes a failure at gateway update even when an user owns the gateway.

Previously, I met following error message.

ag_pov_1  | [2016-12-15 07:52:11,581] [ERROR] [syndicate:1106] (93) Internal err
or Code: -32603, Data: User '4506416817130434844' does not own gateway 'ag_pov' 
(4506416817130434844)
ag_pov_1  | Traceback (most recent call last):
ag_pov_1  |   File "/usr/bin/syndicate", line 1103, in main
ag_pov_1  |     result = client.ms_rpc( rpc_client, method_name, *args, **kw )
ag_pov_1  |   File "/usr/lib/python2.7/dist-packages/syndicate/util/client.py", 
line 272, in ms_rpc
ag_pov_1  |     ret = method_callable( *args, **kw )
ag_pov_1  |   File "/usr/lib/python2.7/dist-packages/syndicate/ms/jsonrpc.py", l
ine 434, in default
ag_pov_1  |     return self.request()
ag_pov_1  |   File "/usr/lib/python2.7/dist-packages/syndicate/ms/jsonrpc.py", l
ine 533, in request
ag_pov_1  |     raise Exception('%s Code: %s, Data: %s' % (result['error']['mess
age'], result['error']['code'], data))
ag_pov_1  | Exception: Internal error Code: -32603, Data: User '4506416817130434
844' does not own gateway 'ag_pov' (4506416817130434844)
ag_pov_1  | Help for 'update_gateway':

[jcnelson]

Thanks!