Refactor gRPC error handling in northbound interface

api/go/gosdn/app/app.pb.go

...sdn/configurationmanagement/configurationmanagement.pb.go

api/go/gosdn/csbi/csbi.pb.go

api/go/gosdn/networkelement/networkelement.pb.go

api/go/gosdn/plugin-registry/plugin-registry.pb.go

api/go/gosdn/pnd/pnd.pb.go

api/go/gosdn/rbac/rbac.pb.go

api/go/gosdn/rbac/role.pb.go

api/go/gosdn/rbac/user.pb.go

api/go/gosdn/topology/routingTable.pb.go

api/go/gosdn/topology/topology.pb.go

api/openapiv2/gosdn_northbound.swagger.json

api/proto/gosdn/app/app.proto

...sdn/configurationmanagement/configurationmanagement.proto

api/proto/gosdn/csbi/csbi.proto

api/proto/gosdn/networkelement/networkelement.proto

api/proto/gosdn/plugin-registry/plugin-registry.proto

api/proto/gosdn/pnd/pnd.proto

api/proto/gosdn/rbac/rbac.proto

api/proto/gosdn/rbac/role.proto