Remove support for empty NI name per gRIBI spec.

[robshakir]

  * (M) compliance/compliance.go
    - Update tests that do not explicitly specify a network instance
      name for the default network instance name to include one.
  * (M) server/server.go
  * (M) server/server_test.go
    - Update reference server implementation to remove the handling
      of an empty network instance name.

See openconfig/gribi#34 for details of this change.

[xw-g]

There are still places implicitly set the default instance, see below. Do you want to change them too?

• gribigo/server/server.go

  Line 251 in 0aae099

  masterRIB: rib.New(DefaultNetworkInstanceName, ribOpt...),

• gribigo/server/server.go

  Lines 828 to 830 in 0aae099

  	if ni == "" {
  	ni = DefaultNetworkInstanceName
  	}

[robshakir]

Thanks! Somehow I missed the latter one. Let me fix that!

On the first one, that is just creating the default RIB on the server (rather than the expectation in the API) since we do not ingest a configuration on the reference server to tell us what the name should be.

[robshakir]

Thanks - removed the rewrite in modifyEntry. PTAL.