list: Implement listAllInterfaces

list: Implement listAllInterfaces

This is not that ideal as API for other objects, as it's still
O(n). Because interface driver uses netcf APIs to manage the
stuffs, instead of by itself. And netcf APIs don't return a object.
It provides APIs like old libvirt APIs:

   ncf_number_of_interfaces
   ncf_list_interfaces
   ncf_lookup_by_name
   ......

Perhaps we should further improve netcf to let it provide an API
to return the object, but it could be a later patch. And anyway,
we will still benefit from the new API for the simplification,
and no race like the old APIs.

src/interface/netcf_driver.c: Implement listAllInterfaces