RFSG attribute methods use inconsistent parameter name

[Greg Stoll]

Specifically, here's a sample request:

message SetAttributeViBooleanRequest {
  nidevice_grpc.Session vi = 1;
  string channel_name = 2;
  NiRFSGAttributes attribute = 3;
  bool value = 4;
}

but RFSA and most other drivers use attribute_id instead of attribute.

AB#1724759