provider/digitalocean: Ingore resize_disk on the import DO droplet tests

```
% make testacc TEST=./builtin/providers/digitalocean
% TESTARGS='-run=TestAccDigitalOceanDroplet_importBasic'
% 2 ↵
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2016/10/25 11:39:26 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/digitalocean -v
-run=TestAccDigitalOceanDroplet_importBasic -timeout 120m
=== RUN   TestAccDigitalOceanDroplet_importBasic
--- PASS: TestAccDigitalOceanDroplet_importBasic (56.04s)
PASS
ok
github.com/hashicorp/terraform/builtin/providers/digitalocean56.049s
```

builtin/providers/digitalocean/import_digitalocean_droplet_test.go

@@ -23,7 +23,7 @@ func TestAccDigitalOceanDroplet_importBasic(t *testing.T) {
 				ImportState:       true,
 				ImportStateVerify: true,
 				ImportStateVerifyIgnore: []string{
-					"ssh_keys", "user_data"}, //we ignore the ssh_keys and user_data as we do not set to state
+					"ssh_keys", "user_data", "resize_disk"}, //we ignore the ssh_keys, resize_disk and user_data as we do not set to state
 			},
 		},
 	})