Currently, get_config_dict provides the sub-config at 'path', by passing the path argument to show_config. This results in
1) the behaviour cited in T2662 through the interaction of the backend and configtree
2) adds an additional dependency on, and call to, the vyatta backend
3) sacrifices control of the result
As an alternative, it is suggested to add a utility function 'get_sub_dict', and apply that to the full config_dict obtained from show_config, for a non-empty path.