Removes `model` as a configurable attribute in instance networking.
Also adds missing `name` attribute from `ip_reservation` docs
```
$ make testacc TEST=./builtin/providers/opc TESTARGS="-run=TestAccOPCInstance_ipNetwork"
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/04/06 12:53:13 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/opc -v -run=TestAccOPCInstance_ipNetwork -timeout 120m
=== RUN TestAccOPCInstance_ipNetwork
--- PASS: TestAccOPCInstance_ipNetwork (258.69s)
PASS
ok github.com/hashicorp/terraform/builtin/providers/opc 258.721s
```
```
$ make testacc TEST=./builtin/providers/opc TESTARGS="-run=TestAccOPCInstance_sharedNetworking"
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/04/06 12:58:43 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/opc -v -run=TestAccOPCInstance_sharedNetworking -timeout 120m
=== RUN TestAccOPCInstance_sharedNetworking
--- PASS: TestAccOPCInstance_sharedNetworking (253.15s)
PASS
ok github.com/hashicorp/terraform/builtin/providers/opc 253.180s
```
