add the capability in the config tag to avoid error

[x0velin]

trafficstars

error received on IOSXE 17.12.02 before adding the capability in the config tag : ''' ncclient.operations.rpc.RPCError: {'type': 'protocol', 'tag': 'unknown-element', 'severity': 'error', 'info': 'config\n\n', 'path': '\n /rpc/edit-config\n ', 'message': None} '''