Add additional datastore import test

Make sure the user gets a helpful error if they only
provide a single ID when running import.

```
$ terraform import hpegl_pc_datastore.my_datastore badID
Error: import has invalid datastore id format

Provided import ID "badID" is invalid. Format
must be "<hci_cluster_uuid>,<datastore_id>". For example:
f8d3e2fd-a0e0-41a3-83b3-a8f92b21a9f3,e8beff7c-6fc8-42f4-bb9f-8e2935d69918
```

test/datastore/datastore_test.go

@@ -237,6 +237,37 @@ func TestAccDatastoreResourceMissingClusterId(t *testing.T) {
 	})
 }
 
+func TestAccDatastoreImportBadId(t *testing.T) {
+	config := providerConfig + `
+	resource "hpegl_pc_datastore" "test" {
+		name = "mclaren-ds19"
+		hci_cluster_uuid = "126fd201-9e6e-5e31-9ffb-a766265b1fd3"
+		datastore_type = "VVOL"
+		capacity_in_bytes = 17179869184
+		cluster_info = {
+			"name": "5305-CL"
+		}
+	}
+	`
+
+	expected := `import has invalid datastore id format(.|\n)*698de955-87b5-5fe6-b683-78c3948beede`
+	resource.Test(t, resource.TestCase{
+		ProtoV6ProviderFactories: testAccProtoV6ProviderFactories,
+		Steps: []resource.TestStep{
+			{
+				// Import
+				ExpectError:  regexp.MustCompile(expected),
+				Config:       config,
+				ImportState:  true,
+				ResourceName: "hpegl_pc_datastore.test",
+				// Invalid id (not "<cluster id>,<datastore id>")
+				ImportStateId:      "698de955-87b5-5fe6-b683-78c3948beede",
+				ImportStatePersist: true,
+			},
+		},
+	})
+}
+
 func TestAccDatastoreResourceMissingName(t *testing.T) {
 	config := providerConfig + `
 	resource "hpegl_pc_datastore" "test" {